Because of that, I would suspect that perhaps the value in strFile is suspect for some reason? Maybe you should print out what you are getting and confirm there is a file there, etc? Perhaps for some reason the file is locked or you don't have permissions to it? (doubt that is the case since you'd probably have other issues as well!)
Set f1 = fso.OpenTextFile(strFile, 1, False, -1)
Couple thoughts here worth verifying:
strTname = "C:\Temp\" & fso.GetTempName Set f2 = fso.CreateTextFile(strTName)
(The First true signifies to overwrite existing files, the second true indicates you are writing in Unicode.
Set f2 = fso.CreateTextFile(strTName, True, True)