Please consider using the Support topic you started, as the problem is not reported by anyone else and it seems very unlikely to be a bug. Rest assured that in case your support topic proves there is a bug in SMF related to this, it will be reconsidered.
Until that, I will merge this topic to the support topic, for the moment. Please can you still consider to provide a test account, normal member account, so we can test eventually with different browsers and see if we can replicate anything?
Please also tell a list of the mods you have installed.
Also, do you have .htaccess file(s) in your web directory or SMF directory?
Also, can you please copy paste the errors in your forum error log, here.