TOPCAT needs your help!!!!

[topcat]

hi all ..i have helped alot of you guys out in the past. now i need your help..
i have had my ps2 since xmas and had it chipped by playstationmods.com...thing is i go to load a game today and the disk is rattling round with very disturbing noises..ar2 disk will load sounds fine but when i put the backup in thats when it starts rattling..now the stupid thing is if i stand the ps2 on its side it work fine no problems..boots everything you chuck in it..can anyone share any knowhow on this one it hasnt been moved bumped or abused in any way .. i cant see it having a loose wire as it works perfectly upright . i know i could just put up with it standing vertical but its not the point . somethings wrong....
please any advise would be gratefull.......

(TOPCAT)