Updated from 6.0.10 -> 7.0.1 on Ubuntu 10.04 64-bit over the weekend, and I am seeing the following problem whenever the web client tries to save a draft of a new email:
system failure: java.lang.ClassCastException: com.zimbra.common.mime.MimeBodyPart cannot be cast to com.zimbra.common.mime.MimeMultipart
This is really making the system unusable since it tried to save a draft ever 15 seconds or so.

Please help!