Motorola Defy+ — Phone lags to a great extent... and Videos doesn't play in Browser.

I have got my hands on the new Motorola Defy just a week earlier. During first three days.. it ran smoothly. But, after i installed some apps from the Android Market, it started lagging and sometimes hangs/ become unresponsive while using and show an alert notification (Task manager) stating 100% CPU usage. Sometimes, it takes about 15 seconds just to open the contact list.

Also, my browser doesn't play videos on you tube or any other sites.

I have not Rooted my phone and using Android 2.2.