Well, some friends of mine had this problem, after updating to Kubuntu 3.5.5 packages their USB/iPod did not automount like before. At the end we discovered i had a newer libhal (0.5.7-1ubuntu18.1 vs 0.5.7-1ubuntu18) because they did a 3.5.3 -> 3.5.5 update while i did 3.5.3 -> 3.5.4 -> 3.5.5 and the 3.5.4 update adds the newer libhal, so if you are having problems with Kubuntu 3.5.5 and did not do the 3.5.4 update, add
deb http://kubuntu.org/packages/kde-354 dapper main
to your sources and update and you'll see libhal update appear and hopefully fix your problem. Riddell toldme he is going to add libhal update also to the 3.5.5 packages, but meanwhile, try it.
Update 1:Seems that does not work for everybody, sorry for you, it worked for some.
Update 2:Seems that Riddell already added new hal packages to 3.5.5 repository so this is not needed anymore, just update and [dist-]upgrade.