[exim] Sudden problem - exim failing

Hi,

I have been running exim 4.69 for months with no problems, but suddenly this
afternoon nothing was working and panic.log is filled with entries like

2010-02-17 21:46:50 1Nh23i-0004ro-Ee unable to set gid=100 or uid=1001 (euid=8): system filter
2010-02-17 21:46:50 1Nh23i-0004ro-Ee internal problem in system filter: failure to transfer data from subprocess: status=0100 readerror='No such file or directory'
2010-02-17 21:46:50 1Nh23i-0004ro-Ee Error in system filter: internal problem in system filter: failure to transfer data from subprocess: status=0100 readerror='No such file or directory'

I don't have a clue what has gone wrong - I haven't changed anything that I
know of.

Can anyone help, please?

Thanks.