Hello,
First thing try reinstalling system manager and se if it works. Check if you are using latest version of systems manager.
Also check if you have sufficient hardware resources memory/processing power to run Systems manager on the machine u have installed systems manager.
The other better way to manage your Netapp storage is via CLI. If you are comfortable with linux OS , you could try setting up a admin host for your filers.
You can have secure ssh sessions from admin host to manage your filers.
There are a lot of documents available for setting up netapp admin hosts.
Also I dont think its your filer thats hanging, unless its heavily loaded than it can handle. I assume its the systems manager software or the system running it is the culprit.
You can also try directly loging into the filer via putty / console and run sysstat -m to see overall CPU load on the filer. If you are seeing cpu loads > 90% than it could cause filer to respond slowly. I am sure you dont want to unnecessarily reboot your production filer and take down time.