Is your weather file located in C:\DIVA\Weather Data\? If so, what happens if you run Rhino as an administrator and re-run the location command (right-click > run as administrator)?
I've never experienced this problem before, so sadly I can't give an immediate answer. Which EPW file are you using? If it is one that didn't come with DIVA, can you upload it here? And does using a different EPW file work?
I am experiencing the same issue as Anastasia, but I am using the EPW file as attached.
Hope this may be of help to you.