Such encryption can be cracked with one of the few supercomputers or with a very large distributed computing effort. It’s a matter of whether or not the cracking needed has a high enough priority for the time and resources required for either kind of effort. And if so, likely a matter of weeks.
And with such an effort, BTW, only one instance of encrypted data is cracked—not the encryption scheme.
Probably not weeks - think ‘eons.’ ;-0
Just over 10e77 combinations in a 256 bit key.
Here’s a fairly easy read on the topic — http://www.eetimes.com/document.asp?doc_id=1279619