Specific instance: I edit a file with IDLE, hit F5, and Windows pops up
a box with a white X in a red circle followed by "Runtime Error!" and an
explanation that the application requested to be closed in an 'unusual'
way.  

Clicking OK on that bring up a similar box. For the current incident,
this has title "t1.py - C:\Program Files\Python30\misc\t1.py:
pythonw.exe - Application Error" and contents "The exception unknown
software exception (0x40000015) occurred in the application at location
0x00d88cef.  Click on OK to terminate the program"

This has happened about three times in the last week since installing
a5. I am not sure if it happened before but it is only occasional (1 in
20 runs?) and I did not use a4 much.  It is possible that this only
happens after sleep or hibernation -- I will watch more carefully.  I
only run pythonw as a side-effect of running IDLE, so I do not know if
that is necessary or not.

As previously, when I reopened IDLE and the the file and ran it
unchanged, I got the appropriate output in the Shell window, as if
nothing were ever amiss.