Can't encrypt files in vista ultimate Sp1

when I try to encrypt any file/folder, the properties window gets busy for a
minute then it gives me the following error message " Access Denied. You will
need to provide administrator permission to change these attributes" with 2
buttons continue and cancel, press either of them doesn't solve my problem
and encrypt the files/folders I want.
well am new to windows vista, just installed it like 2 weeks ago and been
having this problem since then, I installed it myself so my account supposed
to be on admin level.

PS. when I enabled the built-in administrator account on welcome screen and
logged to it I tried to encrypt a random file and it worked smoothly not sure
whats wrong with the other account any hints, advice is much appreciated

Thanks in Advance