Problems with NLB

Hi, good afternoon
I have two servers with CRM 3,0 installed and working with cluster nlb. One
of the frontals, is called CRMFRN01, and the other is called CRMFRN02. The
problem that I have is when from explorer attempt to open the CRMFRN02, is
that it gives an error me that says: Service Unavailable. In eventviewer of
the CRMFRN02, they appear to me the following messages:

Event Type: Error
Event Source: W3SVC
Event Category: None
Event Id: 1059
Date: 3/29/2007
Time: 4:27: 56 p.m.
User: N/A Computer: CRMFRN02
Description: To failure was encountered while launching the process serving
application pool "CRMAppPool". The application pool you have been disabled.

And other event:

Event Type: Warning
Event Source: W3SVC
Event Category: None
Event ID: 1057
Date: 3/29/2007
Time: 4:27:56 PM
User: N/A
Computer: CRMFRN02
Description:The identity of application pool 'CRMAppPool' is invalid, so the
World Wide Web Publishing Service can not create a worker process to serve
the application pool. Therefore, the application pool has been disabled.
The user It has permissions to act like service in the policies of the
sever, and is in the IIS_WPG group. In the other server, CRMFRN01, does not
take place any event and works correctly whit the himself user.

I thank for all the aid to you that podais to give me
Thank you very much