I just realized that if a person attempts to submit a comment on my blog, they will receive the following error message.
Comment Submission Error Your comment submission failed for the following reasons: Invalid request
I don't know where to start to even start trouble shooting this. Any suggestions provided would be much appreciated.
Thanks
Reported on Movable Type 4.2

Did you upgrade from MT 4.1? I had an identical problem while sifting through my comments templates and trying to bring things up to date and get them just so and get things like comment preview to work. Turns out it was a problem of having this:
onsubmit="if (this.bakecookie.checked) rememberMe(this)" [doesn't work]
instead of this in the comment template:
onsubmit="return mtCommentOnSubmit(this)" [works]
I think it relates to what version of the javascript you have...or something.
Of course, there could be other reasons for the error, but that was mine.
I had a couple of issues the last two days with comment failures. I ended up re-uploading the comment response template and that took care of it. Very weird. I got tired of waiting for my host to troubleshoot the problem and just started with the templates first and got lucky.