Hardware problems

About 2 weeks ago I put together a new machine with an AT motherboard (I had
a wonderful Enlight case).
It was working fine for 2 weeks.
Then I put PNY PC100 128MB memory into it.
Now it doesn't want to start.
After multiple power ons/offs, it will finally come up.
Before it had 2 64MB PC100 generic DIMMS.
Do you think the 1 128MB PNY PC100 DIMM could be screwing it up?
Thanks for any help.
Mark