Upgraded to Lion: Time Machine spends a LOT of time indexing backup
From your situation, it's hard to tell if this is normal or if the process is somehow stuck.

You can monitor what is happening from the Time Machine system preference while the backups are taking longer than expected.

For more detail - fire up the Console.app and type backupd in the String Matching / filter control. You might be able to determine if the process is taking a lot of time deleting old backups or something else. You'll also see the timing and the volume of data that might help if you are having slower transfer over the network than before.





Good luck hunting down a cause...

[Edit - responding to additional details on the mount aborting - index failing to get ready.]

OK - this likely won't fix itself. It's always nice to follow the recommended systematic steps to troubleshoot time machine, but I might start first with a verify pass of your existing backup files.

To verify, hold the option key and click your Time Machine icon in the menu bar - the verify process should get you a more concrete error you can understand or it might just fix the issue altogether. Your mac is timing out waiting for a preliminary steo to finish and it's not clear why.