Before making posts I get into overtype mode when making corrections.

Does that automatically happen after a period of time while writing posts?

Is it a new problem?

The only time I've ever had that happen it's always turned out I hit the wrong button on my keyboard - I think on PCs it's the insert button - and I then hit it again to switch it back to a normal mode.

Hope that helps - but I could be wrong and it could be some other problem.