activation server error code: e_adept_request_expired

hi

can anybody please help. i keep getting this error anytime i try to authorize my computer. i have tried all kinds of advice, including changing the date on my computer but that has help. i am using adobe digital editions version 3.0. the full error message is:

Activation Server error

code : E_ADEPT_REQUEST_EXPIRED http://adeactivate.adobe.com/Activate 2014-08-21T11:24:49-07:00%20(14086454890000)%20is%before%20before%202014-08-21T11:55:09-07:00%20(1408647309993)

Please someone help me.