PyCharm won't break on exception

This has been getting more and more frequent, and now is continual.  I have Exception breakpoints enabled on all exceptions, with "Suspend" checked.  Line-number breakpoints work, but exceptions (index out of range, divide by zero) don't.  This is making PyCharm pretty useless as a debug tool.

Happens even for trivially small scripts, e.g.
foo = [1,2,3,4]

results in this:
C:\Users\19529\AppData\Local\Continuum\Anaconda3\python.exe "C:\Users\19529\AppData\Roaming\JetBrains\PyCharm 4.0.5\helpers\pydev\" –multiproc –client –port 53229 –file E:/Python/SubdriveOpt/
pydev debugger: process 10284 is connecting

Connected to pydev debugger (build 139.1547)
Traceback (most recent call last):
  File "C:\Users\19529\AppData\Roaming\JetBrains\PyCharm 4.0.5\helpers\pydev\", line 2217, in <module>
    globals =['file'], None, None)
  File "C:\Users\19529\AppData\Roaming\JetBrains\PyCharm 4.0.5\helpers\pydev\", line 1643, in run
    pydev_imports.execfile(file, globals, locals)  # execute the script
  File "C:\Users\19529\AppData\Roaming\JetBrains\PyCharm 4.0.5\helpers\pydev\_pydev_imps\", line 18, in execfile
    exec(compile(contents+"\n", file, 'exec'), glob, loc)
  File "E:/Python/SubdriveOpt/", line 4, in <module>
IndexError: list index out of range

Process finished with exit code 1

Any ideas would be much appreciated.