Apache 2059 AcceptMutex on Solaris

Running Apache 2059 on Solaris 9. Since upgrading to 2059 from 2055
have been getting intermittent hangs of httpd. Nothing in the error
logs preceding it - the daemon just stops accepting requests.
Changed the AcceptMutex from pthread to fcntl and the hangs have
stopped but now we get intermittent warnings in the error log:
[warn] (45)Deadlock situation detected/avoided: ap_proxy: couldn't
create the lock

This was a known bug with 2.0.55 on Solaris (http://issues.apache.org/
bugzilla/show_bug.cgi?id=32325 )and the reason we started using
pthread in the first place.

However it seems on 2059 that this issue is still apparent but now
pthread wont work reliably either :-(

Does anyone here have any suggestions ?

Thanks