Yes all of us on Domino will occasionally get the dreaded Access Violation NSD errors which hang Domino, usually due to the NBES process.
Some of them are known bugs in the RIM code, some are unknown bugs, but many of them can be eliminated or reduced by doing the following:
UPGRADE YOUR RAM TO 4GB. NOW. DO NOT PASS GO. DO NOT RUSH TO UPGRADE DOMINO OR BES VERSIONS. FIRST GET 4GB OF RAM AND SEE WHAT HAPPENS.
Domino grabs all the memory it can, so high memory usage in itself is not an issue. What you need is to give the server as much memory breathing room as possible so the processes don't step all over eachother's memory spaces (i.e. memory access violations C00000005 errors).
Just my experience, but I sleep better at night these days since running 2GB only servers.