unserialize(): Error on Upgrade from 1.5.6 to OC2.2

Hi! I recently tried to upgrade from OC 1.5.6.4(With Shoppica Theme) to OC 2.2.0 . It did not work out for me, and I got errors. So I thought to revert back to OC 1.5.6.4, but now I get the following error. I would appreciate, if you can be of any help.
Notice: unserialize(): Error at offset 0 of 144 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 50 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 100 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 329 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 9643 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 149 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 259 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 1686 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 48 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 253 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 5 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 75 bytes in /home/proaudio/public_html/index.php on line 67

Notice: unserialize(): Error at offset 0 of 5 bytes in /home/proaudio/public_html/index.php on line 67
Warning: session_start(): Cannot send session cache limiter - headers already sent (output started at /home/proaudio/public_html/index.php:67) in /home/proaudio/public_html/system/library/session.php on line 12

I did not work out for anyone, because it was not meant for, as you could find out, by reading the OC 1.5 to OC 1.5 upgrade info. And if one uses a possibly not longer compatible Custom Theme, additional Problems have to be expected. Sorry for the bad news, but you should have come here, and make yourselfs smart, before screwing up. But unfortunately, you did, at least, hopefully, you made a full backup, of the software and your DB, before ruining your Shop.
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But however the Situation may be, you need to get a hold on pm-netti, or Qphoria, two experienced Upgrade-Pro's around here, possibly able to fix your system again. Mostly not for free, because it's a commercial Software,likely used to generate some income, for Shop-Owners as well as for Dev's.

Good Luck, and don't take it personal, real life consists of learning, mostly by trail and error...
Ernie

HI Ernie. Thanks for your prompt reply. I do not think that this is a theme issue. I had uninstalled Shoppica , I thought of upgrading to OC 2.2.0 . OC 1.5.6 was working fine before I worked on the upgrade. I took the backup accordingly. Apparently, this issue is not script error. I think this is database error, which must have cropped up during the upgrade to OC2.2.0.

I do not mind paying for a professional help. However, I feel these issues have been ignored by the developers, in trying to move too fast. There has to be a reason that OC still has 1.5.6 in the downloads. Most of the people have still not upgraded to 2.X. If it takes more than handful knowledge to get up and running a basic ecom website. We have lost it somewhere.

Well, but why should those issues have been ignored, I don't think, to remember, that ever anybody, from the OC Dev Team at least, pushed anybody to upgrade, MAINLY, because of possible security concerns, or something, making it highly important, to VERSION - 'upgrade' as soon as possible !?

In Contrary, slowly, I start to understand, why this strange looking 1.5 to 1.5 Upgrade info-sheet was still part of it, (or still is?) it should have served the function, possibly, to at least WARN users, that 1.5 won't be V.2, but, as usual, a minority of downloaders did possibly care, but most did not read, or at least, not understand it's content, or Meaning. Otherways, they all would have come here before, to find out, instead of coming afterwards, Just to tell others, that they found out. But since it took so long to me, just to find out the real meaning of the file, I feel with you and, at least, 'understand' your Emotions,to a certain extend...
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But we all know, not only the Oldies, like me, there was not ever one Windows Edition, working in full, at the first attempt. And not one Version of Windows could ever just been Upgraded', by simply overwriting it's predecessor Brand-Version Code on the HD. This, compared to OC, means, that at least MAIN VERSION Changes, such as 1.5 to 2.x, should be accepted as Major Updates/Changes, like from the Win2K to XP, Vista, or Win7. And it's Follower changed everything again..., exept for the (hidden) DOS!

So I believe, one should simply accept it, and smile !
Why ? Because, seriously working enterprises will not act in such foolish ways, when it comes to upgrade a basically
well working money-generator Online Software. They will install one, but Besides, and NEVER in the same Sub, to test first, what is planned to replace existing and working Stuff.

And others have to find out first, how new OC2 works, anyway, so, take it as free gift, you gave yourselfs, and take the chance, to get used with. Nobody else will feel sorry with those Fellows anyway, I assume, at best, they all hate 'em, for acting like a Fool, possibly so destroying a formerly existing source of income...

But nothing personal, I just wrote it, to possibly so keep a few others from doing it. It's getting boring, to always read the same titles, anyway...
all the best !
Ernie

It definitly is a databae error, database is not corrupted, but all tables are rewritten during upgrade.
Hope you also made a backup of your database, if so original site can be repaired.