How to debug session error

My rails (1.1.6) wep application has been working fine for months, with
15 000 user per day. never had any problem with session.

Then I added a new feature to my app, and, after 4 to 6 hours, sessions
start to be lost.
I mean, i set a session["a"] = stuff, at the next call, session["a"]
will be nil !!!
So my user can not login...because of the session["user_id"]

If i restart my application, it works fine for an extra 4 to 6 hour.

If i rollback my application to before the new feature, it works fine.

here is my new feature:

begin
        timeout(15) do
    puts system( EXECUTE AN OPENOFFICE MACRO )
  end
rescue Timeout::Error => err
  log
rescue Exception => err
  log
end

So the new feature is to upload user file, and handle then with an
openoffice macro with a system command...

Sometime, the command fail...

Could it be possible that this command have some impact on the rails
session managment system ?

My session are stored in a Mysql DB.

Please help, any clue are welcome

My rails (1.1.6) wep application has been working fine for months,
with
15 000 user per day. never had any problem with session.

Then I added a new feature to my app, and, after 4 to 6 hours,
sessions
start to be lost.
I mean, i set a session["a"] = stuff, at the next call, session["a"]
will be nil !!!
So my user can not login...because of the session["user_id"]

If i restart my application, it works fine for an extra 4 to 6 hour.

If i rollback my application to before the new feature, it works fine.

here is my new feature:

begin
       timeout(15) do
   puts system( EXECUTE AN OPENOFFICE MACRO )
end
rescue Timeout::Error => err
log
rescue Exception => err
log
end

You may be running into the problem I wrote about here: http://www.texperts.com/2007/05/01/race-conditions-in-rails-sessions-and-how-to-fix-them/

Short version: because you've got such a long running action, it is
very likely that you'll get concurrent requests from the same user and
the different updates to the session overwrite each other.

Fred