wliebenberg,
Like I said, you will have to uncheck the “Show Quick Install Next Time MyEclipse Starts” option at the bottom when this window pops up.
Also, you can go to Windows > Preferences > Install/Update > Automatic Updates and uncheck Automatically Find New Updates and Notify Me.
If the problem still persists, try switching to a new workspace and check if it goes away.
p.s. You will get the update option the first time you open a new workspace and use it. You can follow the above mentioned steps and disable it.