install ing rails

Hi all,   I'm having trouble installing rails onto my machine . i have a Solaris 10 x86 box, ruby version 1.8.6 gem version 1.2.0. when I try to install rails using gems with the command line: gem install rails

It throws this: root# gem install rails ERROR: While executing gem ... (Errno::ENOENT)     No such file or directory - /usr/local=

has any one got any ideas why its throwing this error?

Dan.