Good news - ours fails with the v1 module but upgrading to the new module and doing nothing else fixes the problem. Will try on some other sites, but it looks like the fix is to upgrade to the new version of the module.

Interested to know from Rod what the new module does differently in terms of passing the quote to the url and getting back the response via curl? Besides straight bug fixes how does the module work differently with the new version? Compared the code and there are huge number of differences but suspect most of these are to accommodate the multiple quotes from different carriers...?