I program using MASM32. Twice now I have had to reinstall the MASM32 package. Reason, compiles would not take. If I delete a program the next thing I do caused the fonts to double in size. No I do not have any viruses. I use ESET SS, Ccleaner and Malwarebytes regurlarly. I use the ESET SS firewall. Windows firewall is disabled. I have a ATT router. People on the Masm32 site tell me it could be my AV. Well my AV is ESET. I have no problems like this on my 32-bit puter. These problems occcur on my 64-bit puter. I am running windows 7 pro 64-bit on a hp puter. Others tell me a virus program is not needed at all. With all the crap going on on the internet I find this kind of advice ridiculous.
For your 64-bit system, you need to download a newer version of MASM specifically for 64-bit systems. This may be why you're having issues compiling.