Challenge
While opening nworks UI, you see the following error:
"Object reference not set to an instance of an object"
Cause
The maindb.xml file is corrupted for some reason.
Solution
It is necessary to remove the "maindb.xml" file in the following way:
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Locate and backup file "C:\Documents and Settings\All Users\Application Data\nworks\Management Center\maindb.xml" (for Win 2008 the location is "C:\ProgramData\nworks\Management Center”)
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Stop nworks Enterprise Manager (Management Center) service
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Delete file "C:\Documents and Settings\All Users\Application Data\nworks\Management Center\maindb.xml" (for Win 2008 the location is "C:\ProgramData\nworks\Management Center”)
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Start nworks Enterprise Manager (Management Center) service
Once the service is started again, "maindb.xml" will be recreated.
NOTE: Removing maindb.xml file removes all the vCenter connection configuration, each VEM server advanced property customization, and VEM server ESX cluster assignments.