Hello,
Looks like a simple temporary memory outage. Is the machine under heavy load? Try this patch if you're brave (completely untested). Comments from anyone else? I'm not sure if this is enough or if a more dramatic backoff is required.
The server has two dual-core CPUs, 16GB memory and 6GB swap and is running under heavy load. The swap is not used so it shouldn't be a global out of memory. There only could be a ulimit for the postgresql user.
I will try the patch. Thank you for your efforts. Regards Uwe