Whenever I try to edit forum posts the forum just lags and exits but whenever I do anything else on forums... Anything else it works. (only time my edit works is when I Just made the post)

Try to right click on the edit button and then choose open in a new tab, tell us what happens

Not exactly sure whats going on for you, but a lot of the time the forum lags for me when I hit edit on my post. Double clicking it usually forces it to work for me though.

^ This.

Also try doing it with another internet browser, tell us how that goes.