Ubuntu :: Can't Install Apps In Software Center

I've just upgraded to 11.04 and loving it but, now I can't add any apps through Ubuntu Software Center. I select an app and then click Install. After that, I get this:

An unhandable error occured There seems to be a programming error in aptdaemon. The software that allows you to install/remove software and to perform other package management related tasks.

Then this window pops up:

System program problem detected Do you want to report the problem now?

Now, when I choose to report the problem, I get another window:

the program "aptd" closed unexpectedly. I tried to use

Code:
sudo apt-get upgrade
,and errors
Code:
javi@javi-Cpu:~$ sudo apt-get upgrade
Reading package lists... Done

[Code].....