spannersatcx,
Hi - The file you refer to is a common 'library' file (basically a sub-routine) which many applications use and put in your system directory. Windows will allow an over-write of this file provided it has been approved by Microsoft. Often the problem is a corruption, however.
There are a couple of ways of resolving it - depends on time:
1. Re-install the programme that doesn't work i.e. IE5.5
2. Search any install disks or CD ROMS from other apps for mscvrt.dll - copy it to your system directory (specifically the place where the current one is), and select over-write.
Either of these will work - or put it this way - it's never failed for me.
Regards