Hope you've sorted out your prob. You can find the answer at the Xandros froum - it is hidden in one of the xandros administrator's guides. I cannot remember the exact solution as I'm using Mepis now but the basic problem is that Xandros adds X1 or similar to the end of it's kernel header. run uname -r and you'll see. You have to do something with extraversion to enable the source that you installed have the same header but I cannot remember what.
As I said the answer is definitely in the Xandros forum.