Can you try changing the extension of the downloaded file from .dmg.mdlp to .dmg and see if this helps.
Also, did you download Flash Player Installer file from 'Safari'? if yes, can you try downloading this file from Mozilla.
wow, thanks man, it worked to change to just dmg, I hope you get good money for doing this
We are seeing this behaviour often with users that have MathLab installed and we are investigating why this is happening. FWIW, this happens to other software DMG files as well, not just the Flash Player installer. For some reason, when users have MathLab installed, when the DMG file is downloaded, it appends the .mdlp extension to it. When users attempt to launch it, instead of being opened with DiskImageMounter, which is what OS X uses to open DMG files, it opens using MathLab and the result is what you posted. If this happens in the future, just delete '.mdlp' from the file name and DiskImageMounter will open the DMG, instead of MathLab.