Internet Explorer 5.x may appear to stop responding (hang) when opened but the animated globe in the upper-right corner of the browser window may continue to spin and you may receive a "Detecting proxy settings..." message in the status bar. This issue can occur if Internet Explorer is trying to locate a proxy server.

In Internet Explorer 5, Proxy Auto-Discovery is enabled by default, and this feature may make it appear as if Internet Explorer is not responding.

For more details please see MS KB article Q220902:

http://support.microsoft.com/support/kb/articles/q220/9/02.asp