There is a special 2.10NA firmware beta release on the D-Link Canadian web site: »
www.dlink.com/ca/en/supp ··· =ca_revb that seems to fix the problem with the guest WiFi feature that was borked in the original 2.10NA firmware release.
I have been testing it for several days now, and so far I have been able to have both the normal and guest WiFi SSIDs enabled with no WiFi connection problems.
The Canadian site seems to get the new NA firmware fixes and releases first. I also recently found the version 1.04NA firmware for the hardware version A1 DIR-601 at: »
www.dlink.com/ca/en/supp ··· =ca_reva which greatly enhanced IPv6 capabilities, and also toned down some of the unneeded debug messages when using the external syslog feature (the log is now actually usable).