Have you conifigured the following:
1.E1 controllers
2.Bandwidth on all Serial interfaces.
3.Virtual template and
4.Loopback interface.
Especially the virtual template and the loopback interface has to be configured with great care. Please refer to the following sample configuration for more details.
Sample Configuration - Inverse MUX Application using Multilink PPP
http://www.cisco.com/warp/customer/131/7.html
Check out for the following also :
Restrictions for the dialer max-link 1 Command and MPPP
http://www.cisco.com/warp/public/131/dialer-max-link.html
Hope this helps.