Ran into the following problem when trying to update Avast Free Antivirus from 12.3.2280 to 17.5.2302, in W7 Pro:
-01 First tried via Avast Free AntiVirus 'ProgramUpdate' option
-02 After update W7 was unworkable, programs could hardly be started
-03 Restore W7 backup image
-04 Programlist: uninstall Avast
-05 reboot in safe mode
-06 run avastclear (version 17.5); at the end message about incompatible
EmsiSoft AntiMalware and advice to uninstall; did not (yet)
-07 stop Comodo Firewall
-08 run offline version of Avast Free 17.5.2302
-09 same result as before, hardly workable W7
-10 Via Windows programlist selected avast to try a repair; get errormessage
"an error occurred during removing, possible already uninstalled"
However, program was still in ProgramList.
-11 tried steps 05-09 once more, no luck
-13 boot safe mode
-15 uninstall EmsiSoft AntiMalware V2017.5.2.7600
-16 normal boot
-17 install 17.5.2302_offline
-18 Avast installed proper en W7 was usable, worked perfect.
-19 because of the BSOD once more restored the W7 image backup.
-20 Uninstalled EmsiSoft AntiMalware
-21 Stopped Comodo Firewall (just for safety)
-22 Used the Avast 'ProgramUpdate' option
-23 installation went ok and W7 also works OK.
Conclusion: It seems like EmsiSoft software is causing the Avast Update to fail.
But of course I'm not sure of that.
Maybe EmsiSoft AntiMalware could be re-installed now, did not (yet) try that
Have send this report to Avast as well.