Thread:Project:Support desk/Error creating thumbnail/reply (2)

I think your thumbnailing is broken. The reason why some images work, is that they are already so small that mediawiki doesn't try to downsize them. In this case I think its most likely an issue with missing image magick (aka the convert command), or mediawiki not having permission to run the command, etc. If you could post the debug log (See Ciencia's link Manual:How to debug) that would help identifying the problem. In this particular case, I don't think its $wgMaxShellMemory, since usually (not always) that has a non-empty error message.

If you absolutely cannot fix it, you can use $wgUseImageResize = false; which will prevent all scaling (but makes users download biggger image files).