Can reproduce it with Dev300m39 on WinXP and Fedora

How to reproduce it
1 Open a new document like Writer, Calc etc.
2 View - Toolbars - Form Controls, click "Push Button", drag and draw it in the
  file
3 Select the button, right_click and Control, Properties Button dialog opens, 
  switch to "General" Tab, "Label:Test", "Take focus on Click: Yes";
  switch to "Events" Tab,click button at the end of "When receiving focus" 
  line, "Assign Action" dialog opens, click "Macro" button and OOo Dev 
  Macros - PythonSamples - TableSample - click OK on Macro Selector dialog, 
  click OK on Assign Action dialog, close "Properties Button"
4 Click "Design Mode on/off" button to turn off Form controls bar
5 Click the button inserted at step 2

Result
An error dialog opens

Expectation
Click "OK", it is no use

Note
After step 5, if click "Design Mode on/off" button to make all of buttons on 
Form Controls bar active, then hit OK button on the error dialog, it works very 
well.