After an update to 11.04 the fans of my Inspiron 9400 go in overdrive and never lower speed. Is this normal? It did not happen on any of the other Ubuntu releases.
I'd suspect you have one process taking one of your two cores. This raises the frequency to the maximum and this in turn raises the speed of the fans.
So you could can kick off the system monitor (you still have a good response time because the second core is not hogged up).
See if one of your processes takes 50% CPU. If it can be killed, kill it and see if the fan takes a break.
If so then you will still need to figure out why this process is spinning the CPU.
My 1720 has perfectly working fans in 11.04. I did do a new install though. But instead of advising a reinstall have a look at this: http://www.ubuntuupdates.org/packages/show/305155
Install that and see if that daemon works!