This thread was helpful to me at first b/c I was having the same problem with my 7100i...so I just assumed that I was on the 3.6 version. I later found out though that I am on a BES 4.0 not the 3.6, so I am still wondering why my address book, tasks and memo pad are not synching. Still on hold with the "blackberry expert" at nextel. He has told me that I should uninstall the desktop manager and reinstall (which I saw that jontalotta said I shouldn't use to synch up with) and if that didn't work to contact my server.
So much for the BB expert. Thank you for any additional help in advance!