Won't Turn Over

This is an odd problem that I am having problems trouble shooting.  I am running an Athlon Processor with a ECS K7s5a motherboard, 256 crucial and 512 kingston RAM.  I built the computer about 2 years ago and everything has been running fine until a couple months ago when I turned the computer on and it won't get passed the initial boot screen that checks the memory and IDE devices, it would just stop at that screen after verify the hardware profile and won't let me enter setup. After waiting overnight and turning it back on it seemed to work.  This has happened now about 6 times.  Each time it is different and I have no idea when the computer will boot back up.  I changed memory slots, took out memory, unplugged on IO devices, tried to reset bios, and everything else I could think of.  The hard part about it is that all of a sudden it will turn on and work perfectly for a month or so then it goes out again for a day or two.  This is very inconvenient considering all my work is done on this that computer.  My guess is that the motherboard is going out.  Has anyone run into a situation like this or might know how to fix it?