Try the simms in a different mac if you have one. Or replace them - maybe with something smaller just for testing purposes.
Also - have you had your power supply recapped? Unstable power could be causing your problems, perhaps. If the voltage isn't high enough, or there is too much ripple coming out, it could cause something like this. This would also explain why Uniserver says it works... He tested i'm sure using a fixed / recapped power supply.
Regardless of whether this problem is being caused by the power supply, I highly suggest you have it done before turning it on again. Otherwise, you'll just over-stress the computer and perhaps kill something in the process.
Also - have you had your power supply recapped? Unstable power could be causing your problems, perhaps. If the voltage isn't high enough, or there is too much ripple coming out, it could cause something like this. This would also explain why Uniserver says it works... He tested i'm sure using a fixed / recapped power supply.
Regardless of whether this problem is being caused by the power supply, I highly suggest you have it done before turning it on again. Otherwise, you'll just over-stress the computer and perhaps kill something in the process.