Hi Caitlyn and welcome!
I'm not an expert by any means, but something must have happened. I've never heard of having trouble after they got along for a while. I know my dogs get more aggressive with our cat when we have dog visitors who are aggressive. I guess its the pack instinct. Hope you get it worked out.
Logan

[This message has been edited by lhg0962 (edited December 01, 2000).]