From ebay news board:

***Resolved: SYI/Bidder and Seller Search***
Date: 11/02/03 Time: 07:00:59 AM PST

The ability to search by Bidder or Seller (by clicking on Search in the header and clicking on the By Bidder or By Seller tabs), and the ability to view items you were selling or bidding on through My eBay or your bidder or seller’s lists were temporarily unavailable. Some members were also receiving intermittent errors while going through the Sell Your Item process.

These issues have been fixed, and all features are working correctly.

Thank you for your patience.

Regards,
eBay