The underlying issue of bad files being created by apt, not update-manager, in /var/lib/apt/lists/ has been resolved in Quantal and is being resolved in 12.04 LTS. This is being tracked in bug 346386.
However, the original description that "update-manager can't handle hotel web access pages" is still true. update-manager with the fix for apt in place will tell you that it was unable to download a package and to check your internet connection. If connectivity checking is available update-manager should use that to present the user with a more informative error message.
The underlying issue of bad files being created by apt, not update-manager, in /var/lib/apt/lists/ has been resolved in Quantal and is being resolved in 12.04 LTS. This is being tracked in bug 346386.
However, the original description that "update-manager can't handle hotel web access pages" is still true. update-manager with the fix for apt in place will tell you that it was unable to download a package and to check your internet connection. If connectivity checking is available update-manager should use that to present the user with a more informative error message.