After 8 hours and less than 1% backed up, I disabled Spotlight, and it finished within a minute.
Spotlight did have my external disk in the Privacy list, but when i re-enabled it, it was gone. I put it back in and now everything seems to be playing nicely.
I disabled it using the directions here http://http://osxdaily.com/2011/12/10/disable-or-enable-spotlight-in-mac-os-x-li on/
I just had OS X 10.7.5 reloaded onto my computer (after an "upgrade" locked the computer and it wouldn't reboot)....and bought a new external drive to do my TM backups....so now I'm doing my first full backup (couldn't transfer my old backups to the new drive....see separate post ) and my computer has been sitting here for 5 hours and has only done 400 MB (out of 225 GB)....wifi should have nothing to do with it as its simply backing up directly to an external hard drive...
What's going on?
After failing repeatedly to transfer my existing TM backup (on case sensitive drive) to a new, larger HD I gave up and decided to start again.
External WD Passport 2 TB drive - partitioned to Extended Journaled, this time case insensitive.
Speed test on the drive itsef connected via USB gave me write speed of 84MB/s. I'm not enough of a techie to understand how this might correlate to actual backup times. However, for 300GB (the amount of data I have to backup) and based on the speed test, a full backup should complete in ~1 hour.
I start Time Machine.... TWO DAYS it says.
Reading through this thread, I ran the TM Diagnostic via Terminal. Reformatted the drive and started again.
Initially read said 5 hours. Huge improvement over two days. After the first 10GB transferred (which took about 10 minutes) the estimate is now down to 4 hours; now 15 minutes in I seem to be at a consistent 1GB per minute transfer rate.
I have no idea what the benchmark for this tranfer should be but I can live with 4-5 hours a lot easier than two days. So, the TM Diagnostic is at least worth a try in my opinion.
I subsequently went in and disabled Spotlight via this --> http://osxdaily.com/2011/12/10/disable-or-enable-spotlight-in-mac-os-x-lion/
The backup is now 45GB complete (after running for 44 minutes) and the estimated time to completion is now ONE HOUR.
So, there's that.