Yay, I sorted this one. Probably a horrible fix but if you're interested...
OK, this is how I fixed the “The procedure entry point MtxCluGetDtcUserInfo could not be located in the dynamic link library MTXCLU.DLL.” error on the server
The problem is to do with the MSDTC subsystem rather than ADO itself. Lots of things within Windows use this system so when it breaks it actually can affect quite a bit of stuff, but anyway, I digress.
There is a technet article that explains re-installing the MSDTC but unfortunately running the relevant command simply gives the same error as above. This is because the command tells msdtc to uninstall itself, but if it is broken it can’t do this. I fixed it as follows:
Firstly, locate the file “dtcsetup.exe”. This will probably be in c:\winnt\system32.
Run it from a command line as follows:
Dtcsetup /C /T:C:\dtcsetup
This will just extract all the files to c:\dtcsetup rather than trying to install it.
Next, stop some services. You need to basically try and stop any service APART FROM THE FOLLOWING:
-Alerter
-COM+ Event System
-Computer Browser
-Distributed File System
-Distributed Link Tracking Client
-Distributed Link Tracking Server
-DNS Client
-Event Log
-IPSEC Policy Agent
-License Logging Service
-Logical Disk Manager
-Messenger
-Net Logon
-NTLM Security Support Provider
-Network Connectors
-Plug & Play
-Remote Procedure Call
-Remote Procedure Call Locator
-Removable Storage
-Security Accounts Manager
-Server
-System Event Notification
-Task Scheduler
-TCP IP NetBios Helper Service
-Windows Management Instrumentation
-Windows Management Instrumentation Driver Extensions
-Windows Time
-Workstation
Don’t worry if some are missing, or some won’t stop, just do your best...
Next, do a search for “mtxclu.dll”, ensuring you have got the option to search hidden/system files switched on. When the search is complete, delete (or back up to another PC) all the files found. This is needed otherwise Windows File Protection will simply replace your “fixed” ones with the broken ones.
Next, copy all the files from the dtcsetup folder into \winnt\system32, overwriting any that are present.
At this point, Windows might flash up a WFP warning saying to insert the CD as files have been replaced - it is important to choose "Cancel" here, else it just puts the buggered ones back in again.
Reboot and you’re done!
(the only other step I did, which I don’t think is required, is to run “msdtc –install” from a command prompt within the dtcsetup folder, and I also right-clicked on “dtcfull.inf” and chose “Install”. I did both these before the file-overwriting procedure and they didn’t help, so skip ‘em for now.