Q:

Oracle SQL Developer not responsive when trying to view tables (or suggest an Oracle Mac client)

I just get the beach ball all day long (it's been doing nothing for hours).  It's not taking CPU, not reading from disk, not using the network. 
I'm using Java 1.6 on Mac OS X 10.5.4.  It worked once, now even restarts of the computer won't help.  Activity Monitor says it's "(Not Responding)".  Only thing that I can do is kill -9 that sucker. 
When I sample the process I see this:
    mach_msg_trap        16620
    read        831
    semaphore_wait_trap        831

An acceptable answer that doesn't fix this would include a url for a decent free Oracle client for the Mac. 
Edit:
@Mark Harrison sadly this happens every time I start it up, it's not an old connection.  I'll like to avoid running Windows on my laptop.  I'm giving some plugins for my IDE a whirl, but still no solution for me. 
@Matthew Schinckel Navicat seems to only have a non-commercial Oracle product...I need a commercial friendly one (even if it costs money). 

A:

I get the same problem after there's been an active connection sitting idle for a while.  I solve it by restarting sql developer every once in a while. 
I also have Toad for Oracle running on a vmware XP session, and it works great.   If you don't mind the money, try that.