Installed GIMP Portable 2.6.11 over an existing 2.6.10. Tried to open a JPG file from XnView in GIMP, error message: Unknown filetype.
Trying to open the file from within GIMP: GIMP does only see XCF files, click on "all image files" - same behaviour, only XCFs are displayed. Click on "all file types" shows JPGs to, but opening the file leads to the same results - unkown image type.
Same problem with a clean install of GIMP Portable 2.6.11.
Now I switched back to the backup of GIMP Portable 2.6.10, works well.