Wireless & PPTP Disconnects

Hi

I use a Wireless Lan to connect to the office trough PPTP. I have two
notebooks, both with WinXP Pro and latest Service Packes installed. With one
notebook I have no problem, but with the DELL Inspiron 510m I can connect to
the office. Open a remote desktop but the connection closes just after
5-30minutes.. it's really different...

I tried connecting trough cable, this works perfect.. only when I use the
wireless.. has someone an idea what that could be?? the wireless settings
are the same as on the ibm notebook with 3com card.

Thanks
Patrick