Epox 8RGA+ motherboard problem...

Dear all:

My PC with Epox 8RGA+ motherboard has been working just fine until
recently for some reason, after a hot day of weather (maybe), the
motherboard simply won't post. Now I'm getting some LED code (on the
motherboard) C1h (Detect Memory) or C3h (Expand compressed BIOS code to
DRAM), sometimes 29h (*). Sometimes if I turn off the switching power
supply for a while and if I got lucky, I "might" get the motherboard to
post, but it's not consistent and usually it simply won't post. The
monitor was tested ok, the switching power supply was also tested OK (I
think). I'm wondering what could be the reason? I have took out all the
PCI cards that attached to the motherboard. Although this computer is a
bit old (bought in 2002), but I was using all quality products
(switching power supply: Enermax 365Watt), memory is Corsair 512MB x2
(CMS512-3500C2PT, rated at 433Mhz), and retail AMD CPU (AMD Athlon XP
3200+ with factory cooling fan). From your experience, does this sound
like a memory problem, CPU problem, or motherboard problem?? I don't
have any spare AMD CPU or DDR memory to switch for testing. What would
be your suggestion for trouble shooting?? Many many thanks!