>> After a bit searching around I realised that Google Earth had uninstalled itself.
>> I re-installed Google earth and everything is working fine now.
AFAIK Google maps doesn't need Google Earth - I'm on a linux box without the latter, and maps works fine. However I did notice Google and Gmail seemed slow at times yesterday.
www.theregister.co.uk/2010/04/27/earth_view/
Google Maps absorbs Earth view
Google Maps yesterday got a new tab - an "Earth" option which injects all of the meaty goodness of Google Earth into the search monolith's online cartographical offering.