yes i think the problems in market started around same time when paid apps was enabled for Msia.

now, some of my installed free apps don't appear in My Apps, but if i search for it in the market, it shows as installed. this makes updating a real pain because the notifications wont appear anymore, i have to search individually for it.

i tried using market enabler to fake US telco, then all the apps appear.....

titanium backup is the undisputed best. but a lot of functions which may be daunting for beginners. you have to take your time to play with it. i used it to transfer all my apps from old phone to new phone. no need to go abt installing everything again.

my backup pro also quite good. but very simple and lacks functions. good for newbies.

settings > privacy > factory data reset.

beware, everything will be wipe off