This may or may not be the same problem:
last night I uploaded a photo (via Add Image - Create New link from left margin of someone else's album). After completely filling in the Add Image Form and clicking submit, there was a long delay. DNS found Summitpost, and the browser (very old version of Firefox) status bar said something to the effect of "uploading data to www.summitpost.org
" for a while, which is normal since I was uploading an 8MP photo over a not-always-great wireless network to a not-blazing-fast cable modem. I stopped paying attention, but a few minutes later a window had appeared that had the Summitpost header up to the blue bar, but was otherwise blank except for the text of an error message (something like "database error: object not found", but I don't remember clearly). [Edit: After reading the top of this thread I think it may in fact have been "no database selected". Keep that in mind if you're ever on a jury.] I hit the Back button, clicked Submit again, and it worked fine (after a similar delay). Later I discovered I'd created two Image pages, but on one of them the image was not visible (medium size thumbnail did not exist -- I didn't try clicking through to see if the original full-size image existed). I deleted that page.