A newer version may resolve these freezing issues in Windows 7. We were able to replicate the freeze on one of our own Windows 7 machines and this fix (revised version Nov 3, 2010) was able to get things back to normal and running smoothly--and also fixed some video issues that were popping up (e.g., videos not appearing or not continuing to the next item upon completion).
The link to the update is www.empirisoft.com/download_old.aspx
Please let me know if it helps!
Blair
PS., Kristen, take a look at the "x" parameter in the users guide. It allows you to turn an ordinary instruction item into a secure password screen. For an instruction item, e.g., adding the parameter (xcat) will require the password "cat" to continue. You can also set a global password for all experiments in the MediaLab Preferences section for versions 2008 and later. You can also search on "password" in these forums and I expect you can find more discussion of this vs custom html passwords and passwords via Advanced Features. The x parameter is WAAAY easiest.