This problem has to do with the way W2003 handles standard output. I beleive it has been resolved in Tcl 8.4 available with Cloverleaf 5.4.1+
As a work-around:
When you exec a command
If you need to look at the results of the command, redirect the output to a temp file then read the file contents. If you do not need the output of the command, redirect the output to null (nul:)