Strange error "host: isc_taskmgr_create: no available threads"

Dear Srs,

I'm getting this error on a Linux box, running Apache 2.0.52:

"host: isc_taskmgr_create: no available threads"

Making some search for those strings in Google, didn't tell me anything about this.. appears to be related to SELinux, but it's disabled in the box.

Any idea about this error? It's appears to be something related to ISC libraries...

Regards,