I know you posted this back in November, so this is probably all moot now. But it sounds like the early stages of a red ring of death. The Console is getting too hot and knocking itself out. Microsoft have already admitted to a variety of reason for this happening.
Check the serial and date number on the back, if it's within 3 years of console manufacture, then send it back and get a free box back with better internals (Jasper chip) and a fresh 3 year guarantee. Also, because of the increased number of RROD reports Microsoft have extended their warranty, but haven’t really made it public. (I've transferred 4 boxes out of warranty and got free replacements on all.
Don't open it, it's really not worth it and voids you getting any new boxes from Microsoft.
T