update of OSX Yosemite 10.10.4 created the trackpad not to respond to finger touch, only to hardware clicks?

iMac 14,1 Intel Core i5

OS X 10.10.4 (14E46)

Ever since I update my iMAc with the latest OSX Yosemite, the trackpad doesn't respond to finger-touch as click, nor to second clicks.

Before I could finger touch 2 times to open mail or to open directories in FINDER.

Now it demands two hardware cliccks (through pushes) to respond and often I can nly open mail or directories by seconday clicks which open the menu and to select there "OPEN"..

Has anyone the same experience?

Rohal