stdout handle is finalized

I have a rather large program, and
suddenly, after no changes related to
output, my program "crashes" with the message:

Fail: <stdout>: hPutStr: illegal operation (handle is finalized)

It does (probably) happen when using "ioError" and "Ex.catch"
to catch the exception -- maybe the gc makes a mistake here?

Anyone any idea for a workaround?

All the best,
 Daan Leijen.

(ps. I am not on this list, so please cc)