Weird comp problems

I used to get a CMOS checksum error and i found out it was the DVD drive jumper so no more errors. but if i unplug my computer now it wont post for 30 minutes. this sounds weird but after the 30 mins it works fine..

Very odd.
I would clear the BIOS on the motherboard jumper.
Plug in minimal parts to test.
Check the motherboard battery voltage.
Try another psu.

i replaced the psu already i did everything except check the voltage.