I've run into this problems several times and there is a simple fix. Just open the texture in a graphics program and resize it to slightly UNDER 4000 pixels for the largest side - 3998 usually works for me but if it doesn't try 3900 - that always works for me. Then resave the texture. It should now apply properly.

"Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." -- Bruce Graham