Huge problem with popping speakers! Help.

I got a big problem with my new studio and new setup.

As far as I understand it, the monitors (both left and right) pops randomly
for about 20 minutes when I start up the computer and starts to play music.
Then it dissapears.
The pops are real loud and sounds like they can damage the speakers.
This only happens with the EMU 1212M soundcard, not with the sucky onboard soundcard, intergrated in the computer.

First we thought it was bad electricity in the building (large building with lots of companies working),
but the monitors doesn't pop at all if connected to the internal sucky soundcard or connected to an ipod.
Only when connected to the computer.

I've swapped the PCI-position of the soundcard, but it didn't make a difference.
The power outlets are grounded.
I don't understand. Please help
Thanks

to be clear, you have a huge popping sound card, not speakers. it would most likely be with the sound card itself. this sounds like dc. check your output and see if the dc is constant or if it goes down immediately. those pci surface mont cards would not be fun to repair, send away for replacement.

Are you running balanced to the monitors? Have you lifted the earth at one end?

Thanks alot, I will try the soundcard in my computer at home tomorrow to find out if it is working or not.