I too encountered these problems. Did some investigation and worked out that this is because BTS is based on osCommerce 2.2 MS2, rather than osCommerce 2.2 MS2 Update 051113.
The osC 051113 update included changes to support MySQL 5.
As it happens, I just finished working all this out and what changes need to be made today :)
I've been working with Apache, PHP, osCommerce, open source stuff and all that sort of thing for about a week now. I was considering uploading my changes as BTS 1.5g, but wasn't too sure about the etiquette of such things - is it really as simple as making the changes, packaging it up and uploading it? I didn't want to step on anyone's toes. ;)