Event queue events remain in process

[Michael Pokraka]

Hi all,
Not sure if I've asked about this here before, but here goes:
The event queue has a number of items that remain 'In process', even though the event has been correctly delivered, workflow triggered and completed etc..
Been poking around the system for a while, as well as trawling OSS, both to no avail. So far this is having no impact on production other than seeing loads of errors in the event queue admin screen, but possibly more annoying is that one cannot get rid of them either.
 
Anyone seen this before/know what causes this?
TIA,
Cheers
Mike