attributes and discount doesn't work on virtuemart 2.0.20b

[vasia]

Hello,
I have joomla 2.5, virtuemart 2.0.20b and php 5.2.9
Even my attributes and the discount works perfectly in different products when i try to put them in the same product the attributes' price doesn't work.
Can anyone help me?
Please somebody tell me the right path of doing it because i am new at joomla 2.5 and maybe i am wrong from the begining.
thank you in advance.