It in my particular case it also once happened using the Finder when opening a folder containing a video file I just before exported from QuickTime Pro. The Finder in Leopard makes a preview icon using the Quicklook engine. In this case the processes com.apple.quicklook and com.apple.finder together spammed the system.log. The Finder Froze up but this didn’t mean that the video file was bad, as that would normally be my first thought.

I have spent some more time on this topic over the last few weeks, while still refusing to Archive and Install my OS. So, I just kept seeing the problem coming back until recently. Gradually I got closer to the true source, I am happy to report now. Combining new found keywords from various posts, for (re)searching again and again, it eventually brought me back to a surprisingly older thread and one post by forgie (see end of message).

Many people noticed correctly that while this runaway syslogd issue was happening on their Mac, apparently something invisible would gradually fill up all remaining free space on the hard disk. This is true, it being a system log file growing out of hand inside the hidden directory /var/log. Again syslogd is not to blame, it is only doing what an other process is telling it to do.

If left undetected the log can store millions of useless error messages until the file grows to gigabytes in size, A. this is not normal, B. it’s filling up all free space causing even more trouble. If you have somehow been able to kill syslogd successfully, this in some cases seems to thereafter cause the mdworker or mds process (spotlight indexer) to go haywire, for yet unclear reasons because it is not supposed to index any items inside /var/log stil it is related.

Inspection of the end of the affected log file will give you a clue to the application or process ID runing on your own Mac that is the culprit. There are for example reports of an old Mozy version conflicting with Leopard even after being uninstalled with the official installer. So again don’t blame Leopard, don’t blame the Syslogd, don’t blame the mdworker. Find your culprit and remove or update it.

In several cases people found many lines in the log like “OQT_MovieImport fseek_store: tried to seek to ; outside of file”. This clue is a nasty one, very misleading, because the culprit is in fact not the application reporting, but a deeper problem with a QuickTime component. Therefore people start searing in the wrong direction. Quicktime is being addressed (asked to perform a small or large task silently) by various applications, so it explains why there is such a great variety in problem reports.

Now, thank forgie for posting the missing link about removing old/outdates/expired 3ivx media components from his /Library/QuickTime/ on mactalk.com.au:
http://forums.mactalk.com.au/13/43557-itunes-7-6-syslogd-things-going-badly.html#post438724

The problem has not returned since I cleaned out those suspected QT media components much older than the purchase date of my MacBook and obviously not coming from Apple. I re-installed some of them after that, all is fine now QuickTime runs fine. A less drastic fix, it only took me a few minutes.

some other refs that helped to reach this conclusion:

http://emperor.tidbits.com/TidBITS/Talk/1687/

http://discussions.apple.com/thread.jspa?threadID=1517359&tstart=4

http://forums.macnn.com/90/mac-os-x/361819/great-crusade-against-10-5-mdworker/

http://www.spockboy.com/blog/archives/8

http://forums.macosxhints.com/archive/index.php/t-42338.html

Yan