I'm seeing some odd behavior if I use load-balance for the pool strategy under 2.4.1.
I'm mining on EMC and Ozcoin. If I use the default failover pool management strategy, I get a rejection rate of 0.4% or lower with either EMC or Ozcoin as the primary. If I use load-balance, my rejection rate goes up to around 4 or 5%.
I believe this, at least partially, because of Merged Mining. You get allot of Namecoin Long Poll's. On Ozco you can disable NMC LP's, don't know about EMC but I would check and see if disabling NMC LP's helps.
Sam