Weird error that corrupts database

[bsmooth]

I tried to add an item to the cart in localhost and generated a Technical Error alert popup. See image error1_b.png

Then all subsequent product screens generate a php error. See image error2.png

I have tested my localhost files on another database backup to make sure it wasn't the files, and found no errors. Then switch back to the database giving me errors, and I was able to replicate it.

What worries me is such a error corrupting the whole site completely.