mac pro not responding

I accidently knocked the cord out of the back, now the start button is flashing white, no response from machine when hold button down..fixxed, sorry..another query? anone have a problem wikth the memory slots in mac pro? i have 8 500mg chips 4 in each tray, but only 2g are recognized by machine..ithe bottom tray is loose compared to the top, which is very snug

Read and try this:-

Intel-based Macs: Resetting the System Management Controller (SMC)

Keep us posted?

When left for a few minutes it worked fine..however I am now concerned with the memory (not recognizing)...in system prefs it says I have 2 g, both in slot A...meaning slot b, the one thats not clicking in place , is the problem..anyone come across this before?