I have also had exactly the same error this morning. I'm running AVG 2012(free version), TMG v7.0, Win7 64bit. My tmgss.exe date is 26Dec2007 size is 673,040 I checked a backup computer of mine that is running the same configuration and the second I accessed the TMG folder with this program I got the AVG virus warning. I suspect the AVG is wrong.
I'm also encountering this hanging on the progress window at 20%. I made the changes to the .ini file as suggested and now I can get into TMG. Running TMG v7.03, win xp pro sp3. Just to test the problem I clicked the "Message Manager" under the "Help" and the problem reoccurred. For now the .ini change has disabled the automatic call to Message Manager and I can access my data, so I'm happy! Just putting in my two cents so that the guys and gals at TMG know that this problem is wide spread. John