Did you recently upgrade to SM2012? Are you using Visual Studio?
Try reloading the controls in visual studios from the SMControls.dll library from wherever you installed the SM2012 console (or even the management server).
I had similar trouble and basically I removed all SCSM control references from Visual Studios. Next I copied all of the SM2012 DLLs to a directory on my development machine. Then I re-added the controls to Visual Studios using DLLs from that directory..everything
worked as expected then. It's not a very elegant solution, but it worked. (It would be safer to simply reference the DLLs from the console installation directory or the managemet server so when patches are released you'll be referencing the latest DLL
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