Time Machine backup slow

Hi:

I have been using Time Machine Editor for the last 8 months to backup my Macbook Pro to a Seagate GoFlex drive once in the middle of night. Been working fine.

Recently I took my Macbook to a different country for 2 weeks. I came back and now the backup after 9 hours is still only half done.

I cleaned up the drive a bit and mostly I removed files as opposed to adding them. Since I was away I would expect the backup to take a bit longer but that is crazy. The last successful backup is still the day before I went away.

Why would it be taking so long?