5
That's it!
It should the right answer to this problem!
I was also had this problem, after changing it to GD2 in the preference setting of xcGallery, it is corrected.
Besides, the reasons for the display of debug information is that XOOPS is in default being set to debug mode, just go to general preference of the administrator module, check that about in the middle of the page, there is an option to turn off the debug mode <-- do it and you'll not see the debug information.
Corrected Now??