RAAD: Not able to connect to 'computername'. Initialization error

Hello, 
I'm having trouble connecting RAAD (v2.1.24.0) with four desktop PC, that have XP SP3 installed. 

The Message error is, "Not able to connect to 'computername'. Error de inicialización" (Initialization error).
I've tried several things locally (Firewall, MS Updates, Running Services, .NetFramework, Uninstalling & Deleting Agent from DB, IP/DNS).

This error also ocurres on Altiris Administrator machine, when trying to connect RAAD to this workstations.

Any ideas or suggestions will be appreciated.

Thanks,
Ezequiel.-