401 Unauthorized

I'm runnig vTiger 1.0RC5, and I'm looking for an answer to this: Every now an then, no matter if I'm actively logged in or I'm busy doing anything else, the site returns a "401 Unauthorized" and refuses to get me into the User Interface. Also, when I try to regain access to the application, a box pops up asking me to provide a Login and Password because -it says, I have no rights to see the content. No matter which user name/password I use, I can't not pass from this box again.

After a few minutes, everything backs to normal.

What could be the problem here?

I don't know of any reason a

I don't know of any reason a JumpBox would behave this way. It sounds like there's something else on the network that is interfering with the connection. A proxy server, content filter or maybe another device competing for the same IP might have this effect. Is there any possibility that something like this is possible?