XF 1.3 Creating a post yields an error

Today I've been trying to post on my forum, and I've been successful, even after dealing with internal server errors. I'm running XenForo 1.3.3, and this error seems to be happening only to myself unless nobody else has told me about it.

When I go to post, I click on Post Reply and I'm given this message:

I'm not quite sure what I should do to fix this. I don't get a server error log in the ACP, nor do I get one in the cPanel error log area.

Edit: Posts do show up after this error, but I'm not sure why.