I have just installed Meteor version 0.5.9 (45fef52095) to my CentOS release 6.3 (Final) server (Linux version 2.6.32-279.19.1.el6.i686 (mockbuild@c6b8.bsys.dev.centos.org)
Using meteor reset erases all the data from your database. If you're worried about this then navigate to your project folder.
meteor reset
cd /path/to/my/project
Here you need to erase the mongodb.lock file.
mongodb.lock
rm .meteor/local/db/mongodb.lock
Now you can run Meteor using the command,
meteor