[quote user="ReinierC"]I can try this, but I do feel its quite pointless to upgrade to CCS 5.5, only to downgrade the compiler version.[/quote]
the compiler version is pretty separate from the CCS version. You could have upgraded the compiler version without updating CCS.
Updating the CCS version is always good to get various IDE and debugger fixes
[quote user="ReinierC"]What external factors, besides the anti-virus software, could have an influence on the compile time?[/quote]
I guess the big question here is why you noticed such an increase in your build times. Nothing jumps out with your build options assuming you are indeed using the same optimization settings as before. I'm assuming your actual external environment didn't change much (same PC with the same anti-virus, etc).