Not 100% sure what you are doing..
If you plug a USB drive into the TC and use archive.. it will backup the whole TC.. the TC is without any decent backup.. it is by design a backup target for TM not a place to store files. So it is not made to be backed up.
Time Machine cannot backup the TC. and the sparsebundle cannot be backed up as an incremental backup due to its disk image nature.
Please explain further if I have it totally misunderstood.
What are you trying to backup exactly and how??
sorry if I didn't explain this correctly.
I use an external drive, which I plug in to my work machine in the day and then take home to plug in to my home machine at night.
My home machine has a time capsule which is set to backup this external drive.
Up until recently, the time capsule would only backup new or altered files from the external drive. But just recently the time capsule has been carrying out a complete backup of the drive (so 480GB of data) on each sceduled backup.
OK.. that is a bit clearer..
Firstly this has absolutely nothing to do with Time Capsule.. it is hardware.. a dumb as a board hard disk in the router.
The issue here is Time Machine which is an extremely complex piece of software.
It is set to do incremental backups always.. except the very first backup.. if it is doing full backups of the drive it maybe something wrong.
I recommend you load the widget onto TM so you can see what is going on.
Is there a parallel directory on the disk or something like that very large that the computer cannot open..
Please open the disk in finder and see if it is all readable.. verify it from disk utility.
You might also want to verfiy the backups.
There are a number of reasons backups are too large or doing whole backup instead of incremental.. the log messages should tell you what the problem is.
Look at D3 and D4.
Make sure you are using ethernet to do the backup.
If you don't get anywhere.. erase the backups and start over.
I would also reset TM.. to get rid of any issues.. A4
I would also spend some more money and buy a new disk.
I have issues now with Mountain Lion not reading a disk that works fine in Snow Leopard.. I don't understand what is going on.. but as a backup regime surely your workplace can afford something better than this.
Any disk showing errors replace.. You can use it but once a disk shows degradation.. never trust it. Disks are cheaper than ever.. and unless you buy really high standard server types.. are really not long life.. consider 3years a max.. if you are carrying around important info.. replace. A good quality 2.5" is better for carrying around btw.. they are made for laptops and being moved around .. 3.5" drives are designed to be stationary.
And use more than one.. if your data is worth anything.. swap around disks. Plan that if something goes wrong.. you can fully recover, except perhaps the last days work.