It would help immensely if you could tell us which line the code is crashing out on. Basically CDO wraps up MAPI code libraries and presents them in slightly nicer format for VB
to access. The error you are getting there is a pretty generic error being passed back up to CDO by MAPI which is saying "I don't like that". As such, the context of exactly which line is crashing out is extremely helpful.
If, as I suspect, it is crashing out on the line
objSession.Logon "", "", False, False
then what is happening is that your logon profile doesn't have defualt access rights to your exchange server. I'm not sure how you would go about fixing this save for passing Username and password details (as well as maybe the exchange server etc.)
I'm actullay a bit (/lot!) out of my depth here in figuring out what's going wrong for you but will have a dig around if you post back on you error. I can recommed that you try posting on Google groups, which has a MASSIVE readship of very learned people or have a look at http://www.cdolive.com/