Error message: 'computers couldn't connect in the amount of time allotted'

I'm getting the error message: This computer can't connect to the remote computer. The two computers couldn't connect in the amount of time allotted. Try connecting again.'
The computer is a laptop running XP, connecting via remote desktop connection to the terminal server. This always worked fine in the past. Just lately, the user logs in ok, then after 5-10 minutes they are thrown out of the terminal server connection with the above message.
I have numerous laptops of the same spec which are fine. The user isn't trying to log in from anywhere else. There are more than enough terminal server licenses. The user hasn't installed any new programmes. We use an 'all user' policy so their account hasn't been singled out in any way.
Does anyone have any ideas why this is happening? Thanks