Does the de-auth stop if the encryptionis removed?
OK, I did a bad thing... two variables.
I seem to be stable now, but I applied the hotfix listed on this page.
Update for Windows XP (KB893357)
Started from scratch with the router. left encryption off...
Seemed fine. Then re-built my routing table.
Seemed fine. Then added WPA.
Seems fine.
So I think that I am seeing the up-time due to hotfix listed.
To help you (if needed!) I have a 634m and a dir 625 that did not need this hotfix for me to have a solid connection. I will update later to tell you if it is stable long term.