How do I reset the chunk generation queue? It seems to be stuck but not actually be doing anything.

My cpu is at 15%, and my server's is at 21 percent. Ive pregenerated about a 300*300 chunk area with the distant horizons mod disabled while playing with the client side mod on, so I was generating some LODs for chunks client side in that time. Now that Ive turned the serverside mod on again, the queued chunks are still marked red but they aren't actually being generated.