Ruby in Ubuntu 11.10

I keep getting the following alerts for every ruby command on UBuntu 11.10. Any clue how to fix it?

Invalid gemspec in [/var/lib/gems/1.8/specifications/json_pure-1.6.1.gemspec]: invalid date format in specification: "2011-09-18 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/terminal-table-1.4.4.gemspec]: invalid date format in specification: "2011-11-07 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/spruz-0.2.13.gemspec]: invalid date format in specification: "2011-08-17 00:00:00.000000000Z"
Invalid gemspec in [/var/lib/gems/1.8/specifications/json_pure-1.5.4.gemspec]: invalid date format in specification: "2011-08-31 00:00:00.000000000Z"