Thanks - just to rule it out of the equation, please do the following:
Disable this 'marktopics' application (I don't know what application this actually is, so I am not going to assume it is called 'Mark Topics')
Wait a minute
Open up a topic that will trigger this error and confirm, yes or no, if the issue still occurs
Provide a full screenshot of the error being displayed, not a copy/paste or a cutdown version of it, please.