AOpen mobo hangs playing DivX

I have an AOpen motherboard model AX34, chipset VIA 694X that after a
random time playing DivX content hangs completely, even the mouse
cursor stops. I followed a note at DiVX site suggesting to install the
VIA 4 in 1 patch, even tried various versions without any improvement.
Also tried the VIA latency patch. The computer is a Pentium III at 1
GHz, 128 Mb of RAM PC133 and an NVidia AGP video card. I've discarded
the video card trying other cards, even PCI cards, with the same
result.

I use the 5.2.1 codec with Win98 SE, tried some stress programs to
check the board, memory and processor and they are fine, it's just the
DivX codec that hangs. Even playing a plain MPEG file works fine. I've
installed the FFDShow codecs, and using them to play DivX fixes the
problem, but I've got some files that don't play too well with these
codecs. Also tried Windows media classic and Zoom player with the same
result.

¿Any idea what to try next?

This problem seems to happen more frequently when playing higher
bitrate files, but all of them hang sooner or later.

Thank you for your attention