You are running Parallels Desktop version 3, builds 5584, 5600 or 5608
You have downloaded the latest build of Parallels Desktop 3.0 (build number 5636) by Parallels Desktop menu -> Check for updates option.
Parallels Desktop 3.0 prompts to install the update:
When you press “Yes” button Parallels Desktop application blinks for a second, but nothing happens. Update installation does not start.
Double-clicking the downloaded .dmg file results in "The following disk images failed to mount. Image not recognized" error:
Resolution1. Close Parallels Desktop application
2. Double-click the downloaded .dmg file. This time .dmg file will mount and you will be able to proceed to update installation double-clicking on "Install Parallels Desktop":