MN-720 connectivity drops

Have tried to monitor this group to get some help; will
try to post this problem (again) to see if there is
something I have missed.

Periodically, my MN-720 losses connectivity to the MN-700
base station; the MS Broadband utility
reports: "incorrect security key." Only a re-boot of the
base station will correct the problem. I am running XP
SP1 with WPA. Attempted remedies checked (based on
various posts from this group): 1. have installed WPA
twice, 2. have installed the MS wireless "roll-up patch";
3. base station firm-ware, etc. is up-to-date, and 4. my
SSID is less than 20 chars --- all these remedies seem to
have been suggested to this group as possible solutions
to connectivity drops.

Any help appreciated.