If the double clicking on the Home Button doesn't work (needs to about as fast as you would double click on a computer), then you probably have an older version of iOS, pre version 4.x.x
You can check this under Settings >> General >> About >> Version.
In that case you don't need to worry about closing apps, because they close when you hit the home button.
You can also try deleting the apps that are casing the problems and then downloading them from the App Store again. That will only work for apps you got from the App Store. Ones included with the iPad can not be deleted.
If nothing else is working you may have to restore the iPad. We can help with that too, if you keep having problems. Or you can call Apple Tech Support and let them talk you through the process.
If you are running a something older than the 4.3 version you might want to update iOS. I'd get it working first though. I'm not certain that the update replaces everything. Best to start that with a functioning iPad.