Pls HELP! Upgrade error/problem

Hi all Masters

I was upgrading from 1.5 to 1.5.4 & now getting this error on www.e-ciggies.co.nz

On main store error is Notice: Undefined index: serialized in /home/eciggies/public_html/index.php on line 58

On admin page error is: Notice: Undefined index: serialized in /home/eciggies/public_html/admin/index.php on line 42

I am a first timer when it comes to upgrading any help will be highly appreciated.

Thanks

2schaa