Click Internal Settings button.
Scroll to bottom and click Flush Connections button.
This happened to me after a client's Sonicwall reached the maximum number of connections. On the System->Status page the Current Connections was 65536. The maximum connections that this Sonicwall with this firmware can have when using GAV/IPS is 65536.
You can find out maximum connection information by navigating to System->Diagnostics. In the Tech Support Report section check all four boxes and click Download Report. Save the report to desktop. Open report and search for “Max Connections when using GAV/IPS”. Compare that number with the number Status page.
When the maximum connections have been made, the logs should have an entry stating:
The cache is full; 65536 open connection; some will be dropped.
The above was listed for me on the Status page in the Latest Alerts section.