Only one instance of webstorm/phpstorm at a time ?

I have purchased Idea 9, phpstorm and webstorm and have all three installed.  If I am running phpstorm and attempt to start webstorm I get the message "only one instance of webstorm can run at a time".  The same thing happens whenever I have one IntelliJ product running and try to start a different product at the same time, so for instance, when I have IntelliJ Idea running and I try to start phpstorm.

Is there some configuration option that I have missed that allows me to run two different products concurrently ?  I would think someone working in php in phpstorm might also want to have another IntelliJ product opened at the same time.

Thanks for any help you can offer.