As far as I can understand, mint4win is a 32-bits application - and like all 32-bits applications, it might have issues with a 64-bit OS, which in your case is Windows. What I believe is that the "emulation" software - which makes running Mint as a Windows application possible, is unable to run fully successfully in 64-bits Windows, hence your problem - it won't boot Mint.
This is just my pure theory, I might be wrong.
EDIT: Try downloading the 64-bits version of Mint 10 RC, and it should do the trick. Make sure to uninstall the other mint4win before you install this one.
It can be downloaded here: http://www.linuxmint.com/edition.php?id=68