Lync 2013 will not log in if username on domain contains spaces

Hello,

We have just deployed Office 365 and are now trying to use Lync 2013, however we have found that users who have a space in their domain username (i.e. 'John Smith') cannot log into the Lync server:

The Lync client returns the following message: "The server is temporarily unavailable"

Users with no spaces in their domain username (i.e. 'JohnSmith') work just fine.

Is there a fix for this?

Thanks,

Paul