The following script produces a "Tcl_Release couldn't find reference for 0x..." message followed by an "abnormal program termination" when Tcl exits:

        package require XOTcl

        set Interp [interp create]
        $Interp eval {package require XOTcl}
        interp delete $Interp

As you can see, XOTcl is being loaded once in the main interpreter and once in a sub-interpreter.

I'm running XOTcl 1.0.2 with Tcl 8.4.2 and 8.4.4 on Windows.