More info - it is not Vista - I installed ADE on my older PC which I plan to phase out soon (thus eating up another activation on a PC I will be getting rid of - bummer) andgot a similar error. So it must be the Aztac EZ Reader Pocket Pro, which is clarly listed as a supported device on this website. Help.
Update: I have discovered that the sequence is key. if I connect the EZ Reader first, then open ADE, it does not crash. I first did this on the older XP PC, and was able to activate/authorize my reader. I then tried it on the newer Vista PC, where I had downloaded the sample books from the ADE sample library. ADE wanted to authorize the device on the Vista PC, but I cancelled that popup and was able to copy the ADE sample books to the reader and view them on it. I had trouble copying them using ADE, and did it through Windows Explorer, but it seems to work. However, ADE pops up an activation window every time I open it with the reader attached, so I am not sure everything is really working smoothly.
I have activated four devices so far - the 2 desktop PCs, a netbook, and the reader. I am unwilling to see what happens if I click OK on the activation popups that come up every time with ADE and my reader, for fear of using the six allowed up and then something breaking, or having to replace the reader or reload an operating system or something.
My next test will be to actually buy a DRM book, download it and move it to my reader. If that works OK, I will be pretty confidant about it all.
I hope this sequence can help someone else with similar issues.