If I had to guess, the problem is that a single DELETE is too large to fit in the transaction log. DELETE is the wrong tool for the job. A cursor loop reduces the size of each transaction, so they would not overflow the log, but it is still naive.

The correct solution here is to partition the table. The SWITCH out the old partition with all of its data.

http://technet.microsoft.com/en-us/magazine/2007.03.partitioning.aspx