Updating signatures for windows port of Snort

["Catron, Geoff" <gcatron () dtae org>]

Please forgive the elementary question, but I'm new to Snort and attempting
to update my signatures. I'm using the 1.7 Windows port.
I download and untar the files and replace contents of the rules directory
with the new rules files. When I start Snort I receive the following error
message for every ICMP Info and Virus rule:
 
ERROR ==> ...rules\icmp-info.rules(xx): Bad Priority setting "misc-activity"
 
or
 
ERROR ==> ...rules\virus.rules(xx): Bad Priority setting "misc-activity"
 
Snort appears to be running fine, but what should I do to correct the errors
so my logs don't contain all the nulls for these rules?
 
Also, is there a good source of documentation for Snort? 
 
Thanks for any assistance.
 
Geoff Catron