Yeah, it sucks having the post get cut off. It's gotta be a setting somewhere that needs reset. I've been digging and modified one setting to increase the max post length. Hopefully it helps.
In the mean time, do like Capt suggests. Before you hit the "Post" button, hit the "Preview" button right next to it. That way you can see how it looks before posting, and won't have to modify it afterwards. I always do that when I post pictures just to see how it looks.
