[M*rk]

Agreed, its not working properly.

I believe this is a bug in the BB software.  The new post works OK but there is an issue with the reply button on each post.

I've raised a case with the development team of the underlying BB software.

This has also been added to the Change Request list.

I'll keep you posted...

The myBB developers have accepted the fault.

Only affects some browsers (including IE) - as a work round Firefox seems to work...