When attempting to install 7.5 SP1 update, the follow error message occured when updating the Product list
Symantec Installation Manager has encountered a fatal exception and cannot continue
Log files state that it is unable write the Symantec_V2_PL_XML.Zip file
This was an issue with the folder permissions on the Windows folders.
Security inheritance was not working through all of the levels of the Symantec folder directory. Breaking the inheritance at the Symantec Installation Manager folder and changing it to the correct list of accounts causes the permissions to cascade through the lower levels and then you should be abe to run the Symantec Installation Manager.
Symantec Installation Manager 7.x