It could be one of 2 things. If it stubbornly and consistantly refuses to go down to the 'done' button, I wonder if you are playing in windowed or fullscreen mode? You might try switching modes and see if that fixes it.

If the mouse is 'jerky' it could be because another application(s) is running in the background on your computer. Fish Tycoon is very very polite with other applications and will not interfere with their operation, often at the expense of Fish Tycoon's smoothness. On my computer, if my anti-virus is scanning or too many other apps are running I see the 'jerkiness'.

Please keep in touch and let us know if this was helpful. We'd like to figure it out.