Thunderbird not working (libgtk-x11-2.0)

[midnightrambler]

I tried to start Thunderbird. No success:

bash-2.05b$ ./thunderbird
./thunderbird-bin: error while loading shared libraries: libgtk-x11-2.0.so.0: cannot open shared object file: No such file or directory

so i tried "emerge -p libgtk":

These are the packages that I would merge, in order:

Calculating dependencies
emerge: there are no masked or unmasked ebuilds to satisfy "libgtk".

!!! Error calculating dependencies. Please correct.

"emerge -p libgtk2" or "emerge -p libgtk-x11" also do not work. (same error message)

What am i to do??

thanks in advance,
Alex