Failures to start g++ (due to lack of memory) are not reported to the workunit

I'm running a batch of workunits and am getting some of them fail with this message. However when I re-run them they're fine. It's happened more this morning when I'm running quite a few in one go, could it be anything to do with having several compiling simultaneously?

There are also a lot of messages along the lines of:

conversion from string constant to ‘char*’ <WUID>.cpp:65: warning: deprecated

That's repeated a lot for a collection of different line numbers. I don't get any of those on the re-run workunits.