Eclipse not prompting to choose workspace

I upgraded to Juno (Eclipse 4.2) and every time I would re-start, the default workspace was opened even though I set it to work from a different location.

I had checked "prompt for workspace on startup" but it had no effect.

The solution was to run eclipse -clean from the command line.  Open the Terminal app and navigate inside the eclipse package contents to where the actual executable is:

cd Eclipse.app/Contents/MacOS/

./eclipse -clean 

 That sorted it!