Problem with email reader code

I picked up an email reader code project off of www.vbip.com but I'm having a strange problem that has me completely stumped. I'm rather new to programming so this may be a simple fix. I am testing out the project to pull email from a Yahoo account. So far, everything works fine up until I click on the email to be read. I then get an "Invalid procedure call or arguement" that points to the Set Item = mCol(vntIndexKey) line in the CMessages class module. According to VB's Watch window, vntIndexKey becomes "" just before it's called. I'm completely lost at this point about what to do.

If anyone can reproduce and/or solve this problem, I would appreciate it.
Thanks for any help.