Problems with installing new programs

Dear all,

since the update to OS X Yosemite, I have some problems with installing new programs.

I tried to install the Fitbit App to connect my Fitbit to my Mac but the program can't be started after installation. I have the same problem with Blackberry Blend, too. I am able to install it but it doesn't start running.

Does anybody have an idea what's the problem?

Thank You,

Lisa.