2008-02-18 09:57:52 UTC
Just to report back: I have checked this out with Grisoft and they confirm that this was a false positive. They say:
"... the previous virus database might have detected the
virus on some legitimate applications. We can confirm that it was a
false alarm. We will release the new virus update that will remove the
false positive on this application. Then, please update your AVG and
check your files again."
I'll leave it a day or two and then try again to install Marathon 3; I'll confirm if it installs OK without complaint. It seems, however that the installation is safe.
Rob