[RedPimpernel]

I'm a lab admin in a small computer lab with eight 20" iMacs, (and a bunch of unix servers) on the network.
When I log into an iMac, my dock icons are routinely acting weird. Everytime I log in different icons have changed. From normal to a variety of arcane icons (question mark, icons for rarely used programs like R, a brass plate with 4 screws in it, etc.) When I hover over the icon, the name of the original icon's program is displayed, but when I click on the icon, either nothing happens (the ? icon) or the program for the weird icon starts up.
I have tried deleting the dock preferences pane but it didn't help.
This is particularly prevelant when I use different machins. So far only one other user in the lab is having the weird dock icon problem.
Any suggestions?
Another more recent symptom, when I download files from the web they do not show up on the desktop until I click either quit the web browser, or click on teh magnifying glass in teh download window.

[Damien]

How did you image these computers? NetRestore? NetBoot Install? Firewire cloning from disk to disk?
Did you modify the User Template folder in /System/Library/User Templat/English.lproj? If so, did you account for machine specific settings as stored in the ByHosts folder?
When you're logging into the systems, are you logging is a local user? As a network-authenticated user? If network, how are the computers in the lab bound to the network? Active Directory plugin in Open Directory? LDAP?
Are the computers and/or their preferences controlled by an MCX setup on an OS X Server, via Workgroup Manager?
As you can see, there are many ways to manage computers in a lab. Without knowing more about how your computers are being managed, it's hard to suggest what might be happening.

[RedPimpernel]

I will do my best to answer your questions.
Setup new 20" iMacs with original pre-installed software. Named each computer from System Preferences. Chose one machine to be the master. We are using Radmind to manage software across the machines.
I don't know if the User Template folder was modified.
When regular users log in it's as a network-authenticated user. Connected to the network by LDAP. User home directories are stored on a Unix server.

[Damien]

Ok, we're getting there.
When a user logs in, the OS authenticates against the LDAP database, determines that his/her home folder resides on the Unix server and not on the local workstaiton's HD, and so then works to either (depending on your setup) copy that home folder locally or maps the home folder to a mounted sharepoint. The latter is often called "roaming profiles" or "network home directories".
The Dock settings are saved in ~/Library/Preferences/com.Apple.Dock.plist. This file is part of the profile. However, Dock settings can also be pushed out from an OS X Server using what Apple calls MCX settings. You could use Apple's Workgroup Manager software, for instance, to tell a certain group of computers or users to have the Final Cut Pro icon in their Dock, while other users do not get the icon. The two settings "stack" in sense...so the OS will generate a Dock based on the settings in ~/Library/Preferences/com.Apple.Dock.plist and then add any Dock settings pushed out from the server, stored in /Library/Managed Preferences/username
But if you're not pushing Dock settings with Workgroup Manager, then that's just a datapoint that doesn't have any bearing on your situation.
Other Dock preferences are pulled from /Library/Preferences/com.Apple.dockfixup.plist. This file controls the "baseline" of what Apple will put in a Dock for a new user login. In Workgroup Manager, if you've turned off the option for users to be able to add/remove items from the Dock, then a Dock is generated by "mcx compositor" and the baseline Dock is ignored. If no user management is enabled, then the OS refers back to the baseline dock in the com.apple.dockfixup.plist file.
So, the real question here is: are you using OS X Server and Workgroup Manager to manage the settings on these lab computers?
You mentioned your using Radmind. Is there a chance you've pushed out an unclean loadset with a Dock setting in it, so the Dock settings in the loadset are overriding the Dock settings set by the user, or by WGM / MCX? I know I've certainly been guilty of not properly cleaning up my Radmind loadsets before pushing them out and then having unintended consequences--especially when i was first learning how Radmind works.

[RedPimpernel]

We are not using OS X Manger or Workgroup Manager, so those points don't apply. I'll check our early Radmind Loadsets for stray files. We have set up a script that dumps a dock preferences file when we do our Radmind update every week. That seems to fix things for a while.
We think we have narrowed down the cause of the messed up dock icons, to having the same user logged in to 2 different machines at the same time. Current solution is telling people not to do that.
Thanks for all of your suggestions Damien.

[Damien]

Could also be that the Dock settings are being cached somewhere. I'd have to look to be certain--I can't remember if Dock settings are once of the cached attributes of an OS X system. If so, then it might explain what's going on, as the computer is referencing a cache file instead of the correct Dock settings plist. Just a thought...