Hmm, it appears to be what Green has mentioned. But for good measures, can ye try to post what ye were posting on this thread? If it lets ye, it could just be a site glitch. I would recommend restarting y'er computer and see if that fixes it.
Another way to test the theory, which will be pretty meticulous, is to go through y'er post and delete one word at a time to see if then it will allow ye to post. Of course, it may take ye a while depending on the context, but at least ye will 'ave a clear mind once ye find out what 'twas.
I hope I 'ave helped ye out some.