A quick reference point to deal with the ever present SBS Critical Alert that warns of memory allocation gone awry. In truth the Health Monitor threshold most likely just needs to match the correct amount of memory you installed is it is anything above 2GB. Kudos again to the Official SBS Blog which I have a linked feed on the right of this blog.
The short version of the solution is to change the threshold according to these instructions:
To modify the value, do the following:
1. Click START -> Administrator Tools -> Health Monitor
2. Navigate to Health Monitor -> All Monitored Computers -> SBSSERVER -> Small Business Server Alerts -> Core Server Alerts -> Allocated Memory. On the right-hand pane, right-click on “Allocated Memory” and choose Properties. Edit the “is greater than” value to reflect the correct amount of RAM. Default is 2 GB/2147483648 (3 GB = 3221225472, 4 GB = 4294967296).
Allocated Memory Errors After Adding RAM
The Official SBS Blog : Allocated Memory Errors After Adding RAM