Internet Explorer says operation aborted

I've installed WebAS 6.40 Java System on Windows2003 and EP6 SP9.

Sometimes, when I click on User Administration/Roles, I've receive this message:

Internet Explorer cannot open the Internet site http://localhost:50000/irj/portal. Operation aborted.

And EP6 doesn't open the right frame with roles list. If I click on roles menu again, then Portal reloads normally. I have IE 6.0.3790.0

Does anybody had this problem with IE?