I recently ran into issues with my Azure point-to-Site VPN client while connecting from my local machine to a shared drive on one of my Azure IAAS VMs. The error which shows up on using the Windows Azure Point-to-Site VPN client was:
Custom script (to update your routing table) failed (80070490).
I ended up deleting and recreating the Gateway defined on the Windows Azure Virtual Network using the Azure Management Portal followed by downloading and installing a new copy of the Point to Site VPN client for the Virtual Network from the Management Portal. The issue went away and I was able to successfully connect from my local machine to my Window Azure IAAS Virtual Network including connecting to Shared drives on my Windows Azure IAAS VMs using the internal IP address of the VMs.