To run MTA do next.
Right click on MTA/properties/compatibility
now set compatibility mode to windows XP SP 3 and privilege level: Run this program as an administrator.
Do that with GTA also.
Run MTA and it should be fine.
Also try setting DEP(Data Execution Prevention) and set:Turn DEP for all programs and services except those i select.
Click add and find MTA and GTA and add them.
After doing this MTA should work fine.