Orders suddenly all ear as failed/unfinished - paid w Paypal

Hi,

since 2 days, out of the blue, all new orders no longer appear as completed but instead show Failed/Unfinished. But when I look in the error logs I don't see anything unusual. We also no longer receive confirmation mails but we do receive the payment mails via Paypal.

Except for this which is recurring since a few days (but longer than 2 days): PHP Notice: Undefined index: category_id in /customers/5/8/2/ourstore.com/httpd.www/vqmod/vqcache/vq2-catalog_model_catalog_product.php on line 456

I did clean the vqmod cache, but no difference, all orders appear as Failed/unfinished.

I think it's a Paypal problem since that is the only changing element but I don't see errors in the error log.

Anyone having the same issue or a clue where I have to look?

Thanks,

B