Dial-up networking hangs O/S

IHas anyone ever heard of dial-up networking freezing the whole syste, in Win 98se?
We have just installed a ENW internal 56K modem, it is installed correctly with the correct drivers. When we try to test it, by using a phon number to call rather than an ISP, it dials, then after about 5 seconds, the whole system freezes.

It has 233 MhZ CPU with 128 MB SD Ram and plenty of free space on the HDD.

Any ideas how to overcome this problem?