Xamp Control Panel Authentication Popping up

[rwalkerarn]

Xamp is running on a ubuntu server on a school network (using windows servers, active directory ect, probably not relevent but hey..)

I currently have three joomla sites hosted. The domains are forwarded to a static IP. That windows server then either forwards the requests to our windows webserver or our linux (ubuntu) one. All the sites function absolutly fine externally. Internally there is a rather strange problem.

When I log into the administrator section of the site I keep getting a popup asking for my xamp username and password (control panel), either that or its asking for my Ubuntu password for the actual machine. Either way, if you push cancel enough times it lets you onto the page and use it as normal.

Anyone got any ideas what could be causing this?