Do you mean 2.5 GB ?
That will mean the modem running solidly for around 12 minutes or longer. Given that the chips run warm even in idle running the line interface and demodulator at over 50% of capacity for that length of time will certainly heat it up quite considerably and as BatBoy suggests - overheating may well be the cause.
It is not just the Huawei modem that suffers, I have heard of other makes suffering too.
edit to add:
I will get a thermal probe inside my modem, obtain the quiescent temperature of the heat sink and then run a 1GB download, check the temperature, then repeat.
M H C
taurus excreta cerebrum vincit
Edited by MHC (Thu 27-Oct-11 10:08:55)