Signed network packets (a security measure) require packet
serialisation, which means each database lock has to wait for
the previous database lock to go the server and back again.

SBS has network packet signing turned on by default because
it handles user profiles, including group policy objects.

Sometimes you can get most of your speed back by going
through and doing other optimisations. Look at Tony's
Access pages for suggestions:
http://granite.ab.ca/access/performancefaq.htm

(david)