The cross bars on the roof top carrier on my 08 RX are giving me trouble. The mechanism that releases the lock or catch that holds them in place so you can adjust the position doesn't seem to move as easily as when I first got it. I fear breaking it if I force it. Has anyone else had this problem? Is there an easy fix? Sometimes I can not get them to move at all.

 

There were problems with the '04 cars, and Lexus replaced the cross bars (per a TSB) for anyone who complained (most people never use the rack or adjust the crossbars). When I bought my '04 in '06, the bars were the original ones and would not move freely as they should because working the lever on one side would not release the crossbar on the other side. They were replaced for free and I have had no problems since, although I do not move the crossbars much.
I've not read here of such a problem on anything other than an '04. You could have a mechanical problem or maybe just dirt in the works. If you are under warranty, the dealer should repair or replace the bars for you without charge.
Other than that, I have no ideas.