One of our Macs is having issues displaying message text in Mail. At startup, the messages appear normally for a short while, then suddenly "flip" to display all the text as boxes containing question marks. I was able to watch it happen, then retrieved the following line from the system log stamped at the same time:
Jun 2 14:04:22 dyn-144-92-105-238 com.apple.PerformanceAnalysis.animationperfd: BUG in libdispatch client: kevent[EVFILT_MACHPORT] monitored resource vanished before the source cancel handler was invoked
Does this mean anythng to anyone? For what it's worth, it seems to mostly affect email coming from PCs, rarely Macs.
Should also add that I discovered and was able to remove a corrupted, non-essential system font from the machine in question, but that didn't help.