Does IDA detect Visual C runtime automaticaly or not? What does it write to log?...IDA have very good Flirt signatures to VisualC.... if it does'nt recognize some runtime functions it seems that application is not maded by VisualC... May be it something similar... like MS Fortran Powerstation or IntelC...
How old your application is?
If you have a bit old machine (like P-III) you may try to redetect runtime by
http://protools.anticrack.de/files/utilities/fi.zip.....