4 times is very, very unusual.
4 times on two different machines at once would make me guess somebody's been messing around trying to flash the ROM or similar.
(assuming they're both doing the same thing - you didn't actually say that)
If you haven't already, remove and reseat the RAM - probably NOT the problem, but quick and easy to try.
For the record, these are called POST (Power On Self Test) codes.
1 = No RAM installed
2 = Incompatible RAM type
3 = No good banks (MDD needs at least one good SIMM to start)
4 = No good boot images in the boot ROM (and/or bad sys config block)
5 = Processor bad or unusable
So, #4 indicates a ROM issue which almost never happens except as a result of trying to modify the boot somehow.
If that's what happened, you have bigger problems than I know what to do with.
Just because you should, and sometimes it works, try resetting the PMU.
1. Unplug everything - I mean everything.
2. Open the side, find the little red PMU button in the corner of the motherboard in front.
3. Press it once only for a second
4. Plug all back in.
5. Cross fingers.
6. Try to start again.
If that all fails, you next move to testing the PSU