cheers for the reply JUAN
but unfortunatley the problem still persists with the randomly appearing corrupted avatar file, i have to say that the file isnt one of the avatar items on my hdd its something that just keeps appearing for no reason and ive noticed that this seems to occur only after playing forza 4 (the only achievement i have recieved lately which was also tagged to an avatar item reward was the set a time in all rivals mode) and i'm pretty sure its not the HDD as it is only 3 months old and was sent as a replacement for my old one by ms support.
i also did the redownload of my gamertag which was suggested by xbox to do because of the recent gamerscore issue and also had hopes that by doing this it would help with my problem which it hasnt.
but i also have 2 new developments which only occured the other day
problem 1: when i inserted a game into my console which started to load it then requested an update which i was expecting it to do after applying the update i then received a message saying that the disc was unreadable (which i knew was not true as it had just booted up) i then cleared the cache on my hdd and then the game redownloaded the update and loaded fine (note that i have to go through this process everytime i receive an update for a game which is not normal)
problem 2 : now this one has only happened once so far, i was on the dashboard and using the guide feature to view my friends when the console just locked up, i left it for a little while as i thought it may just be a slow net connection for some reason and didn't want to turn it off incase it caused further problems, after 5 mins i then get a message popup saying that the main xbox update for the console had corrupted and had to be downloaded again, i accepted this and the console updated fine as far as i know and havent recieved this message again.
the thing is that if this was a hdd problem i would get problems right away upon turning the console on, but it loads the dashboard and my gamertag with no problems.
at the moment i'm thinking of transferring my profile and all my save files to a usb stick and then formatting the hdd to see if this helps as the brand new hdd i received as a replacement i just inserted into my xbox and started using it as i found that it was already setup and was fully recognized by the xbox (would like a support reply to this question before trying it incase of further problems arising)
these are the steps ive taken so far:
1: redownloaded gamertag (hasnt helped)
2: cleared my cache (hasnt helped)
look forward to hearing from anyone who knows how to fix this issue...