======
      :
      wm attributes . -alpha 0.4; update idletasks
msgBox "debug-1"
      set code [catch {$cmdint eval $m($m(current),$curItm,code)} rc]      
msgBox "debug-2"
      wm attributes . -alpha 1.0; update idletasks
      :
======
I see the following behaviour which I don't understand at all. Above, there's a fragment of code of one of my GUI-programs (tclkit 8.4.19, Windows XP). In the 2nd line, some code gets evaluated by a slave interpreter ($cmdint). Within these code, something gets [exec]uted without a trailing '''&''', thus the program blocks, as expected; "debug-2" does not appear.
'''But after a few seconds or so, the main window . of my program goes into -alpha 1.0 mode.'''
After ending the [exec]uted process, "debug-2" appears, and the main window of my prog is in -alpha 0.4-mode again.

So, after all, who switches my program to - alpha 1.0 in between? Very misterious...