PocketMatrix

I have an older computer I use as a server, and sometimes as I start it up it gives me a POST (pre-op self test) 'Memory Size Error'. At these points if I turn it off and on again, I get no such error...

The Memeory Size Errors half the size of the usable memory. Any idea what could be causing such a phenomenon?

Sounds like a DIMM is going bad if you ask me. I'd recomend picking up a RAM diagnostic such as and running it on each DIMM individually.