That does seem strange. If you are using a java script they may think it violates their policy:

JavaScript

eBay does not permit the use of these JavaScript functions:
Scripts to drop or read a cookie on any eBay page
Scripts to the user from eBay to another page (such as the replace script)
JavaScript Include and iframe
Many people do not intentionally use the above scripts to cause harm. However, these scripts can be used for malicious purposes. Therefore, in the interest of security, we have eliminated the use of these scripts on our site.

Attempts to use these scripts will return an error message that begins: "Disallowed JavaScript/HTML Syntax." If you get this message, you will be prevented from listing the item. Any other JavaScript error is not related to the disabling of these scripts.

Perhaps they can't tell for sure what its doing and so they just disable all scripts...

Chas