"Offlining" files over VPN cause battery error

[RNW]

XP Pro SP3, ThinkPad T60

I've got a user who sometimes tries to "offline" files (using Window's
Offline Files) from a remote location over a VPN. After a period of time
(sometimes 60 sec, sometimes an hour), the machine displays a critical
battery error message, and goes to sleep. Once this happens, the machine must
be restarted in order for it to get an internet connection again (i.e.,
disable/enable of network does not bring network connection back).

(I know that we could find a work around, and that ideally he shouldn't be
offlining files from a remote location... but... )

Anyone else have this problem or have an explanation?

Thanks.