Rails - Jul 2005 - cannot use production_log_analyzer! T_T

I installed production_log_analyzer through "gem",but it comes:

[root@localhost log]# pl_analyze production.log
/usr/lib/ruby/gems/1.8/gems/production_log_analyzer-1.2.1/lib/production_log/analyzer.rb:381:in
`pad_request_name'': undefined method `-'' for nil:NilClass
(NoMethodError)
        from
/usr/lib/ruby/gems/1.8/gems/production_log_analyzer-1.2.1/lib/production_log/analyzer.rb:318:in
`summarize''
        from
/usr/lib/ruby/gems/1.8/gems/production_log_analyzer-1.2.1/lib/production_log/analyzer.rb:257:in
`request_times_summary''
        from
/usr/lib/ruby/gems/1.8/gems/production_log_analyzer-1.2.1/lib/production_log/analyzer.rb:280:in
`report''
        from
/usr/lib/ruby/gems/1.8/gems/production_log_analyzer-1.2.1/bin/pl_analyze:31
        from /usr/bin/pl_analyze:18:in `load''
        from /usr/bin/pl_analyze:18
[root@localhost log]#


did i miss something?

T_T