What does this mean: "mds: (Warning) FMW: event:1 had an arg mismatch. ac:2 am:51" mds: (Warning) FMW: event:1 had an arg mismatch.  ac:2 am:51


This error shows up in my system.log file regularly. Searching on Google turns up few useful results.

One search result points to iTunes plug-ins/add-ons, all of which I have removed with no change; I still get this error.

Since the error is coming from mds I tried resetting Spotlight, but nothing changed. I have also cleared caches, fixed permissions, run maintenance scripts, verified/repaired the file system in Disk Utility, verified Time Machine backups, even did a surface scan of my hard drive. Anything I could think of that might effect the file system and cause trouble for mds.

I'm at a loss. Does anyone have any clue what this means and how I can make it stop?
EDIT: During Spotlight re-indexing (with sudo mdutil -E /), I got a while lot of...

7/20/12 3:27:43.796 PM com.apple.mdworker.pool.1: PSSniffer error: Invalid argument


...and...

7/20/12 3:53:19.098 PM com.apple.mdworker.isolation.0: failed to parse embedded CMap.
7/20/12 3:53:19.098 PM com.apple.mdworker.isolation.0: syntax error, unexpected DICTSTART.


...each repeated many times over in short bursts.

The same error I had before also came up during and after re-indexing.
These are undocumented internal error conditions and most people outside of Apple can't say for sure what they mean. I wish I had a better, more concrete answer, but here are some ways to poke at your system to get a hint at which file is causing these errors to be emitted...

mds == indexing service. rule of thumb == don't f**k with it unless you know what you do. 


Have you reset the spotlight database using any command line tools? (mdutil or mddiagnose) or conventional methods adding/removing directories from the privacy pane in System Preferences?
Does mdutil -s -a
-v say anything useful? 
Disabling dropbox may help narrowing the cause


Lastly, watching for other mds related console output might be helpful.