well on windows seems 2.6.6 do not works so well you may try to install the previous version
http://downloads.sourceforge.net/gimp-w ... -setup.exeIf you prefer the portable is still available the portable version only may be better use google to search were
then seems mostly that in your case gimp run out of memory
you may fix it
1 increasing the resources dedicated to gimp in the gimp preferences (edit/preferences) ...on the Tutorial board in the sticky introductory tutorial to gimp there are the details
2) then
"look at Start|My Computer|View System Information|System Properties|Advanced|Performance Settings|Advanced|Virtual Memory|
Note what value is set for "Total paging file size for all drives"
If you click on Change , It should tell you a recommended size as set by windows. Set that (recommended ) value in the Initial Size box and set double that value in the Maximum Size box.
Generally the paging file size should be about 1.5 times the available ram . You can find this value by going to Windows Task Manager on the performance tab. There you will find the Total in Physical Memory in Kbytes (eg 3406252 if you have 4 GB installed). The difference in available and installed storage is because Windows uses that storage for address translation (real to virtual) and other essential housekeeping tasks."