The links below have instructions for deleting photos.
iOS and iPod: Syncing photos using iTunes
iPad Tip: How to Delete Photos from Your iPad in the Photos App
Another Way to Quickly Delete Photos from Your iPad (Mac Only)
How to Delete Photos from iPad
How to: Batch Delete Photos on the iPad
(With iOS 5.1, use 2 fingers)
How to Delete Photos from iCloud’s Photo Stream
Have you tried connecting the tablet to itunes and deselecting the ticked albums and then clicking apply?
If that doesnt work, create a new empty folder on your desktop. Choose that specific folder to sync photos from. This will remove all your albums and from there you can consolidate your photos a new.