OS X V10.7 Lion :: Unable To Access Older Backups / Dates

At first (all of a sudden out of the blue) I could not enter Time Machine mode for love or money despite clicking on the enter time machine action botton, however I could run a 'backup now' at any point and this appeared to go through as well as the hourly automated ones. Then switching Off then back On Time Machine suddenly allowed me to enter Time Machine; however I am only able to access the finder windows for any local 'white tick' backups which in my case were only for the last several snapshot backups for today... but if I try and access any dates after this right back until November 2011 last year, nothing happens at all and the date/backup markers are completely unaccessible. Incidently, all of these previous 'purple tick' date markers (time machine backups/snapshots on external firewire 800 drive) were accessible before, but know they can't be accessed even though they corecctly index the appropriate dates right back until November.

I'ts worth pointing out that I've had many glitces and random problems since using a Thunderbolt Display which is where the external hard-drive containing the time machine backup is hooked up to. A seperate recent issue is constantly losing sound on the Thunderbolt Display which requires a reboot to get it back temporarily, but this is a seperate issue but may be related if the cause of a number of problems may be originating from the TD.

The external disk drive containing the time machine backup image, appears to be online ok as I'm able to access the drive in a normal manner. Has some kind of special links nature or association relasionship between the Time Machine program and the external drive and backup disk image contained on it been disrupted or broken? If this is the case, can they be re-linked or re-associated?

Info:MacBook Pro 17, Mac OS X (10.7), MacBook Pro 8,3 - Intel Core i7 2.2