Sometimes it's Skype, sometimes it's gmail. I had this problem for a long time at one point but eventually it resolved itself... here's the post i made way back then

http://talk.maemo.org/showthread.php?t=82602

if you keep having troubles, it might be easiest to just log onto skype or gmail on a desktop/laptop and kill the request there. FWIW i didn't have to log onto the desktop to do that. It might be easier to take care of with wifi rather than 3g...or you may have to open the skype app on the phone.