I have been using LinuxMCE for about 10 months and have had some very nasty core lock-up problems. All of a sudden my core would just freeze up, on the keyboard the green led's would be flashing and all my MD's would also be frozen. With frozen I mean the system would not respond to anything; keystroke or moving of the mouse. This happened for a while- anywhere from 2 hours to 2 days that the entire system would freeze up. I went ahead and changed out the power supply, CPU, motherboard, nic cards, network switch, you name it nothing worked. I disabled the flicker screen saver, like many have recommended, added 2 extra 4 inch cooling fans and still the core would just go and freeze up. My final step was replacing my brand new bought 4 x 1Gb of RAM (Crucial Balistix PC2-6400 800Mhz) (which I was sure could not be the problem since it was brand new and even tested OK in the memory test) with a slower 2x1GB DDR2 667MHz. Ever since the memory swap the core has run and and run with NO lock-up or freezing up. I have it running 24-7 and it runs nicely over 2 weeks with no issues.
My Dad is also an avid LinuxMCE user and reported similar RAM problem to me today - that his system became unstable due to a memory.
SO the point of this post is just a quick heads up to anyone with core problems and to anyone building a core to be aware that LinuxMCE is very picky about the RAM you use - I do not know if it was the motherboard/ram combination but a different Ram solved a big problem in my system.
here are my current and working specs for my core
MSI K9N SLI Platinum motherboard
AMD 3.0 gh dual core Windsor CPU
7300GS 256MG Nvidia graphics
2 x Giga Lan onboard
2 Hauppage PVR 150
2x 1 GB 667 MHZ Ram
200 GB PATA Segate for the os
500 GB SATA Samsung for media
Antec EA430 Power supply