In August of 2007, I was diagnosed with sacral sfx. As with the other poster, I thought that it was a groin injury/hernia. I continued to run with minimal pain and then believed the injury to be osteitis pubis. The pains would subside with time off, but would return. As the months went on, I noticed some hip pain, which I believed to be some sort of piriformis issue. Stretching, etc. didn't help, but the pain was manageable until I was hobbled on a routine easy run. I couldn't walk very well, much less run. For 2 weeks, I did "test" runs until my final diagnosis. After that, the doctor said 4-6 weeks off. Of course, I wanted to get back to running quickly and counted my 2 previous weeks of "test" runs as time off. Total time out was 6 weeks, but, again, 2 of that was with some activity.
For me, I truly believe that running on cambered/canted/sloped roads did me in. I always ran out and back courses on rural country roads. Of course, the slope of the road was always down, so my left side was always slightly down slope. On the return portion of my run, again, the left side was always down. Can you guess which side the sacral sfx was on, left side. Since, I have changed some courses and have done more core work. 6 weeks should be enough, but be ready for the phantom pains that will accompany you with your return to running.