Ditto here, guys.
Evan, the file size limits are 1,000 Mb per image and five images per post. If you accidentally exceed that, it does look like the system's hanging on you for a while after which it "rejects" your post. I had it happen to me once and I figured it out when I checked my file sizes.
Big images don't generally look good in this skin, anyway. In the previous skin, a big photo wider than the post's width would pop up as a separate window, whereas in this one it enlarges in-post and it forces you to use a scroll bar from side to side due to the fixed width of all posts.
I don't suppose there's something we can do about that, is there, Alex?