I finally heard back from CJ regarding problems with eBay's code for their search boxes. If you use 'em, you may want to replace 'em or fix 'em ASAP!
Here is their response:


It looks like there was indeed a problem with the code eBay entered for this link, and the cause can be found in the FORM's METHOD.
If you look at the METHOD, you'll see that it looks like:

If you remove the second double quote, everything should work perfectly.

I've updated the code in their account, so you could either make the change manually to the code you currently have, or repull the code from your CJ account.

Supras | Celicas