When you say "wireless problem", does this behaviour only happen over a wireless connection, or is it the same when you connect using copper cable?
telnet signin.ebay.com 443
Good tip there from Shunter - will sort network / firewall problems from browser problems.
Check your firewall settings, both on the Linksys and the Windows Firewall.
"Out of the box", both should support SSL on port 443, so restoring defaults should work.
Other browser things to check:
If you are using a proxy, ensure that the proxy is set to "use for all protocols".
Under Tools / Internet options is the Security tab - have you (or any installed programs) made any changes here to the Internet Zone? Try resetting to default (Medium High), or add the sites to your Trusted Zone.
Similarly, if you (or any installed programs) have made any changes to the Advanced Settings tab, you can Restore Defaults - and if all else fails, you can Reset the entire Browser (at least you can in IE7).
SD