I have a solution (529 characters long), but when I submit it, instead of getting back the page for level 92, I get level 91 again

If I try to warp to level 92 it tells me I can't, which suggests that my solution has been rejected either because it's wrong, or because of a problem server side.
My impression is that the server-side stuff is failing, because both these cases fail:
- a solution of all ones doesn't get the 'You can't click at (x,y)!' message
- a solution of all zeroes doesn't get the 'You didn't turn on the light at (x,y)!' message.
However the length check on the solution is working fine.
Has anyone else seen this problem?
Thanks,
Paul