What size width x height is the image you are working on, number of layers and size of the file in memory?
I think there was a bug in Gimp (windows) that corrupted very large (edit: not sure of size) files. AFAIK fixed so you should update your Gimp to 2.8.20 http://www.gimp.org
I also read that increasing the cache size can help.
As an alternative you could try the development version, 2.9.5 see http://www.partha.com
This can use a different compression method (if you enable it) for Gimp .xcf files which should be more resilient. But it is a development version although for my simple use I find it stable. Downside is the new format is not backward compatible with Gimp 2.8.x
there was a similar question here:
http://www.gimp-forum.net/Thread-Could-n...138#pid138
I think there was a bug in Gimp (windows) that corrupted very large (edit: not sure of size) files. AFAIK fixed so you should update your Gimp to 2.8.20 http://www.gimp.org
I also read that increasing the cache size can help.
As an alternative you could try the development version, 2.9.5 see http://www.partha.com
This can use a different compression method (if you enable it) for Gimp .xcf files which should be more resilient. But it is a development version although for my simple use I find it stable. Downside is the new format is not backward compatible with Gimp 2.8.x
there was a similar question here:
http://www.gimp-forum.net/Thread-Could-n...138#pid138