What kind of proxy is used? The plug-in is unable to filter SOCKS 4/5 connections, so adding the accounts with proxy ports in plug-in manually can break the downloading via these connections.
Version 3.2.1.1 contains no changes related to filtering message headers. You can try the previous versions to check this:
http://antispamsniper.com/dl/3.0/sniper-mui-3.2.0.6.exe
http://antispamsn ...