Is it possible to effectively use WinRunner to test a web based app on a system running Windows 98?

When I playback a script with 100+ lines, IE crashes. Assuming that the problem was due to memory leaks we have upgraded IE from 5.0 to 5.5 and that made no difference. We have even upgraded WinRunner from 7.01(with web add in) to 7.5 and still IE crashes. Yet when I play the same script on an NT machine it works fine.