VisualBuild file becomes empty

[teognost]

I noticed some strange issue -my regular build was not executed through sch task although the sch task reported success code.
When I looked into the Visual Build project log -I discovered no log was created although I have enabled project logging.
Then finally I discovered my build project C:\Program Files\VisBuildPro6\StartBuild.bld is an empty file (size 0 ,when I open it there is nothing inside)
I thought someone played with this file (although only 2 -3 people have access to the build box and they did not touch that file )so I copied again the normal file StartBuild.bld.
After 2 days the same problem appeared -file StartBuild.bld is empty so the build was not executed.
Any idea what could cause this strange issue?
I do not think there is human intervention here...

[kinook]

Maybe something in the build process is writing an empty file? Or some security software quarantined the file? I guess this was working fine for a long time and then just recently started happening? Maybe some recent Windows or other software update is a factor?

[teognost]

exactly,this worked fine for a 2 weeks ,issues started to appear 3 days ago.
I will investigate all of your suggestions and get back...

[teognost]

well-for a long time I used an workaround to get rid of this issue -I have a scheduled task copying the bld file from a remote location to local box -30 mins before the build starting.However yesterday from some reason this did not work -at the build time the bld file was empty.
I really do not understand what is causing this -there is no antivirus installed ,there is no other VBP process making this bld file empty.
I am rebooting the machine 15 mins before the build (so after bld file was recopied from remote location)-but anyway this should not cause any issue.