Changed my GPU to GFX5900 and now I constantly loose my bios

[fickyficky]

A few weeks ago, my creative GFX5700U crashed . I was given a new AGP card under warranty . It's a Creative GFX5900.
Since I've been using this card, my bios looses its settings whenever it feels like doing it . In the morning, when I try to start my computer, the booting fails with no error warning at all. I can't even get into my bios for looking what's wrong. The only thing that seems to help is to pull out the power supply cable and the screen cable . After the fifth deconnection he might even boot.
When the computer fails to boot, the memory count goes very slow. If i'm able to get into the bios, the date en clock is gone to zero.
I already replaced my CR2032 battery on the mainboard, but it doesn't seem to help. I suppose replacing the battery is the same as clearing the CMOS memory??
When I use a replacement AGP-card, nothing's wrong.

Any suggestions?
Please excuse my English

PIII 900MHz intel
384 Mb SDRam (133MHz)
Creative Geforce FX 5900 128Mb (not for production use)
Plextor premium CD-RW
Plextor 716A DVD-RW
Power supply 350W
Mainboard Asus CUV4x-m

[Denniss]

FX5900 uses more power than your old card, maybe the PSU has some problems with the high power usage a start ?

Does your 5900 require an extra power connector ?

[Ritchie]

Thanks Denniss - You just gave me an idea.