We have been using Roundcube for quite some time (since around .2). We are currently on .7.2 stable. We are using Dovecot IMAP as our backend on a Ubuntu 12.04 server, with Apache.
Recently, HTML emails from Zillow.com (a real estate site) are showing up as Chinese characters (if you open it in Chrome, it even pops up an offer to translate). Other HTML emails work fine. If I force the users settings to not display HTML emails, they show in plain text fine. If you open the same email in the same account in Thunderbird (using IMAP) it displays fine (in HTML). I haven't found in the source what is going on.
I tried on our backup machine testing .8 RC, but it has the same bug.
I have attached the message source and a screenshot of what appears to the user (in all browsers). I have redacted/changed some the names, phone numbers, and email address, but otherwise not changed any major portion of the email. If some thinks they have an idea and needs a full, unedited copy let me know.
Edit:
The upload attachment is small, so I uploaded a better quality screen shot to imgur
