Corrupted SSL downloads under IE only

I have a problem when files that get downloaded under IE6 using SSL that indicate they have been changed and are now corrupt. This only happens using IE without Fiddler (a session browser) and does not occur under Firefox.

Using WinDiff to scan the files shows they are in fact markedly different however show identical size.

Turning on Fiddler however and then downloading, the files are never corrupt.

Does anyone know what may be happening inside IE that Fiddler is overcomming and Firefox is
not even doing?