File Sharing checkbox refuses to check

[wowatcmu]

I had set up file sharing between our two macs in our home (both 10.6) with no problems.
But our iMac's disk blew out and was replaced, with 10.6 reinstalled.
Now I find that the iMac can see my MacBook Pro, but when I try to enable file sharing
on the iMac, the checkbox for File Sharing refuses to take a check: it briefly displays
a - sign then reverts to blank. I have triple-checked that the security settings are the same on the
two machines, and that the
file permissions for the listed files are okay (ie, the same on the two computers).

I presume I am missing something on permissions, but I am at a total loss as to what.
I would appreciate suggestions.

 

[wowatcmu]

Answering my own query

A local guru advised me to look at the console when I tried and failed to set file sharing. It turns out that the plist System/Library/LaunchDaemons/com.apple.AppleFileServer.plist had been rewritten as an empty file during the os reinstall. The old plist was saved as com.apple.AppleFileServer.plist~orig, so it was simple to reinstate it and now all is well.