HI Gary,
This is most likley an eBay issue but since you are running Mac OS X (10.5.2) updating your system software might help. The current Leopard Mac OS X is 10.5.8. And from the Menu Bar in Safari, click Safari/About Safari. You need to be running the current version which is 4.0.4. Running Software Updates should get you up to speed.
Always repair disk permissions after an update...
Quit any open applications/programs. Launch Disk Utility. (Applications/Utilities) Select MacintoshHD in the panel on the left, select the FirstAid tab. Click: Repair Disk Permissions. When it's finished from the Menu Bar, Quit Disk Utility and restart your Mac. If you see a long list of "messages" in the permissions window, it's ok. That can be ignored. As long as you see, "Permissions Repair Complete" when it's finished... you're done. Quit Disk Utility and restart your Mac.
And try maintenance...
From the Safari Menu Bar, click Safari / Empty Cache. When you are done with that...
From the Safari Menu Bar, click Safari / Reset Safari. Select the top 5 buttons and click Reset.
If Safari unexpectedly quits, it could be a 3rd party plugins causing the problem. Go to ~/Library/Internet Plugins. Move any 3rd party plugins to the Trash and restart your Mac.