I use IDManager all the time. It is installed on several servers, both Linux and Windows, development and production.
John, just a wag, but I've had issues on more than one occasion with TeamWorks, IDManager, and my own apps if the temp folder for the application on the server doesn't have the proper permissions. Might be worth granting everyone access to it as a test, and if that fixes it then scale back on the permission level (IIS_IUSRS full rights--see picture):

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I had a post relevant to TeamWorks for this a while back.
The other gotcha (which I think you actually posted about a while back) is the Application Pool for IIS. Now I get into the habbit of creating a new one for each application, and setting them to the same settings the IDManager install uses:

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...jack