We noticed that invitations and meeting requests sent from WebAccess contain incorrectly encoded UTF-8 characters in the human readable part of the e-mail invitation as well as in the DESCRIPTION attribute of the ICS file. Here's an excerpt from the ICS file of such an invitation:

Apparently the bug was introduced at some point after release 6.40.0 with the new "meetingTimeInfo" property in the meeting request. The following two patches fix the problem: