Well, obviously Abrasive Rock is going through some changes and, as is usually the case with major changes, when that happens you have to re-evaluate your situation. We were working closely with Mark on some big plans for AR's future, and we just felt that some of the changes that are happening are drifting away from the original direction that we wanted to pursue.
After some discussions with Mark we just felt that it was in our best interest to move on to something that we felt suited us better (for forum hosting at least) and we decided that something was Ultimate Metal. Rest assured, there are no hard feelings between us and AR and we wish all the best for AR's future.