If it's only been a short time since the reboot from the firmware upgrade, I'd give it an hour or 2. If it's been a while, I'd open a support case with Dell Equallogic support to have them take a closer look at the diagnostic files.
Hello.  We have an EqualLogics PS4000 which I upgraded yesterday from firmware v4.3.6 to v5.0.8 and then to v5.1.2.  IT only has one member and no replication setup.  Everything seems to work fine after the upgrades, however, in the logs I am seeing the following error: Level: WARNINGTime:  12/28/11 10:34:17 AMMember:  PSNHQSAN99Subsystem:  SPEvent ID:  28.3.17Active control module cache is now in write-through mode. Array performance is degraded. What does this mean, and how do I resolve it? Thanks, Joseph    
EqualLogics Upgrade Issue