[Typo3] backend partially missing

[Tim Boesenkool]

I have a typo3 3.7 install with about 4 sites running on it. 

Part of the back end has disappeared and I could use some direction in
diagnosing the problem please.

All links from 'Web' and 'File' (page, view, list, template, filelist etc)
are bringing up page cannot be displayed. However I can access pages that
are in my "taskcenter" etc. Which leads me to believe the problem may be in
the directory column.

I've checked all typo3 and server logs and there doesn't seem to be any
apparent anomalies.

Thanks, any help is appreciated.

Regards

Tim