well, take a screen shot of the error message and post it in mantis, come back a few hours, or a day later and try what we say. you are probably not the only person to get this error so it'd be nice if we could fix it.
I was sort of looking around to see if there was some way I could tell if a texture had an alpha channel or not, I'm an OGL novice, so I'll have to yeild to Kazan on that one. as for the small texture thing, I just noticed that myself, I tried finding out why it was doing that, but I couldn't, so I made up a bug report and gave that to Kaz also.
I'd say the big thing we are missing right now is chunk import/export, I took a stab at that tonight, but I couldn't figure out how to get the loading code to work (kaz did some freaky multi-threaded stuff with it to make it run faster, and I have zero multi-thread experience)