Finder freezes when deleting files across a network
What version of Mac OS X are you running?  If you're not on a relatively current Snow Leopard (10.6.x) consider upgrading.  

Relevant log files may be found on your Mac OS X client in the /var/log directory.  These three may (or may not) contain relevant information (depending on what's actually happening):


system.log
kernel.log
secure.log


Consider also looking in the logs on your server, which may give you additional information.

You can restart the Finder (short of rebooting) in a few ways.
(1) log out, and log back in; or,

(2) restart the Finder in the GUI;


open the "Force Quit Applications" monitor window
select "Finder" in the list of running applications
click "Force Quit"
Finder will automatically respawn unless hypothetically something dreadfully broken on your system prevents that, in which case I imagine a reboot might be required (I've never seen that happen)


(3) Restart the Finder in a Terminal shell;
The command you describe would be expected to work, but it looks like the open command on your system is guessing wrong about the nature of the Finder.app path that you gave it. Consider launching Disk Utility and running the Repair Permissions.

Note, however, that the Finder should respawn automatically once it's been killed.  The simplest way to restart it in a shell is to:

$ killall Finder