Perhaps you mean AdSense? As far as I know, you are allowed to have more than one AdWords account. In terms of AdCenter, I do not know - but it would be listed in their TOS.
Even though multiple accounts are not allowed in Adwords.. there are people who are creating multiple accounts!
Multiple accounts are allowed in AdWords as long as they are all under a single My Client Center (MCC) account. As for adCenter, not sure why you'd want 2 accounts - it'll just make everything twice as painful to work with . Call up adCenter tomorrow morning & ask, that's the easiest way to find out.