Another bug found in 126.96.36.199, whenever I start it, i also get an “Interface Not Supported” dialog box.
You may try to delete TDM.txe file from:
C:\Documents and Settings\user\Application Data\Quest Software\Toad Data Modeler\Configs
(This is a default location.)
Then try to run TDM3 again.
Note: I point at another thread below that followed this one: