In BI LaunchPad Dashboard file stuck on "Initializing" phase, just for some users

What could be the cause of this?

This is the issue: When accesing a Dashboard file from BI LaunchPad it gets stuck on "Initializing" phase apparently only if it is accessed by users that were migrated from BO XI r3 to a new system with BusinessObjects 4.0.

If the dashboard is accessed by non-migrated users, -that's new users that were created directly in the new system - it is displayed properly. But if a user that was migrated from the old system tries to access it, even if this user has full permissions even Administrator permissions, it won`t work and the dashboard gets stuck on "Initializing" phase and never shows up.