Loading Symantec installation manager you would immediately get an uncaught exception in application error message
Reviewing the logs you would see the following error:
Uncaught Exception in Application
System.BadImageFormatException (SymantecInstallationManager): Could not load file or assembly 'Xceed.xip, Version=4.311069.16410, Culture=neutral, PublicKeyToken=ba83ff3687563c6' or one of its dependencies. The module was expected to contain an assembly manifest.
The Xceed.zip dll file had become corrupted.
Install Symantec Installation Manager on another machine. Go to the C:\windows\assembly\gac_msil\Xceed.Zip\4.3.11069.16410__ba83ff368b7563c6 directory and copy the Xceed.dll file and replace it on the Symantec Management Platform in the same location.
Note: To get to the gac_msil directory you need to open start run and paste the C:\windows\assembly\gac_msil\Xceed.Zip\4.3.11069.16410__ba83ff368b7563c6 directory into it.
ITMS 7.5 Symantec Installation Manager 7.5.129