Hi.
I'm having the same problem since I upgraded to 1.4.5. I've posted several times here, and several times on Google's Support site, but have had no responses.
I check it occasionally, and it seems to just be going back and forth between calculating it and default. I don't know if it's a sandbox issue or what. It seems that if it were a production problem, there would be a lot more people screaming about it. People must be actively using it, but how it's acting on my end, it's simply not usable. Are you on Sandbox?
The other issue is that it does not allow for first class shipping. It says it allows priority mail, but it doesn't have a place to turn that on, and I have yet to get an answer to either that issue or that of an answer to whether or not they will be adding first class.
I have really resisted PayPal. I have a real bad taste in my mouth with them, but I'm feeling I may be forced to use them, at least for now, because I'm ready to go live in every other way. This is the only thing hanging me up.
If you find an answer to this, please let me know. I will do the same.
Thanks,
Caat