Hello Jens. Thanks for your reply
It is solved now, the card is working fine and I can connect. Here's what happened:
I did run xsurftest booting with no startup sequence but the same thing happened. Then after a few more resets the computer stopped booting completely. I feared something else was damaged so I took it apart and started testing with just the CPU board. It worked.
Then I started adding things one by one until I added the X-Surf in the same slot it was before and again, no boot. I changed the X-Surf to a different slot and it booted again. So I added everything else, leaving that slot empty (maybe it is damaged, maybe it was just bad luck. In any case I don't use it) and all is fine now. All expansions working and internet connection reestablished
Thanks for your help!