IDLE has suddenly become FAWLTY - so should I be hitting it with a big stick, or what?

[Twirlip2]

I've been using IDLE with Python 3.4.0 on Windows XP (SP3), since March this year, and since May I've been running IDLE almost continuously, using it scores of times every day, mostly to run the same script (for running a media player on BBC WMA streams, to bypass the dreaded iPlayer).

No problems, until today.

For a few days, I'd been frequently running a second instance of IDLE, to test a new version of the same script.  Today, having closed this instance, I tried to open one again, but I briefly saw an error message about not being able to create a thread, or something like that. I'd seen similar messages before, but all that had ever been needed was to terminate a few other processes, and try again.  Not this time, however.

I closed the first IDLE instance as well - and since then, I haven't been able to get any instance of IDLE to run at all!

I have tried the following, all without success:

1. Closed other processes, and retried (as just mentioned).

2. Logged off, logged into an admin account, and tried running IDLE there.  Still nothing happened, and still nothing showed in Task Manager | Processes.

3. Installed 3.4.1 (over 3.4.0). It made no difference to the problem. (I also had to do a hard reboot of the system, after it had completely ground to a halt when I tried to reboot in the normal way.)

4. Disabled the router (for safety), then (temporarily) disabled the antivirus program.  No joy.

5. Rebooted, instructed Windows Firewall to make an exception for pythonw.exe.  Still no joy.

6. Downloaded Process Monitor, from <http://technet.microsoft.com/en-us/sysinternals/bb896645>, installed it, ran it, and filtered to show all events having process name 'pythonw.exe', and any result other than 'SUCCESS'. There were hundreds of such events, including many stating 'buffer overflow'. (I'll go into an admin account, run Process Monitor again, and give details of the results, if it will help.)

7. Deleted .idlerc - this had no effect on the problem, so I restored it.

8. Created shortcut with target <I:\Python34\Lib\idlelib\idle.bat -n>, and double-clicked it, with no effect.

9. Ran the same command in a Windows command shell window.  Still no result.

I think that's everything I've tried, so far.  I'm pretty exhausted now, so I thought I'd ask for help.  Any ideas?