Redmine

Hello,
I have a big eror with redmine, I cannot access anymore my git repository.
No one did anything, but redmine can contact it and crashes wit error 500.
Here is log file:

Processing SysController#fetch_changesets (for 192.168.1.2 at 2012-02-15 11:05:05) [GET]
  Parameters: {"key"=>"1QsDEEPJrM2Z2azdWVxnx"}
SCM command failed, make sure that your SCM command (e.g. svn) is in PATH (/usr/local/bin:/usr/bin:/bin)
You can configure your scm commands in config/configuration.yml.
'git' '--git-dir' '/var/www/git_repositories/project.git' 'branch' '--no-color' '--verbose' '--no-abbrev'
with: undefined method `[]' for nil:NilClass

But whereis by www-data user gives git: /usr/bin/git /usr/local/git
And configuration in redmine is well ticked...
Thank you for your help.