Are you experiencing this problem with XP or another OS like *nix?
I had the same problem when upgrading from Ubuntu 7.10 to Ubuntu 8.04. The shortcut under my Applications tab no longer included "Wireshark (as root)".
You can still run it using
Code:
user@ubuntu:~$ sudo wireshark
...which will give you the privileges required for accessing the interface.
It could also be a privilege issue if you're using XP but I haven't had problems with that myself.
Hope this helps!
g0bl1n