I only started battling over the last couple of days. I've been reading through all the guides in the forums so that I can learn the best way to do it.

Anyhow, I keep having this recurring problem when I go to battle and get this message... "Oh No! You are trying to equip an item (Gear Theme Crossbow, tier: 3) that is above the tier of your pet (1)!"

I don't understand as my battle pet is a T3 and I double check that he is my Active pet, but also he can battle no problem most of the time, but every now and again this message appears. Sometimes when it appears and I check my pets, my battle pet has disappeared from my list of pets to battle with, and I'll go back and try again and he has reappeared!

I'm really confused, can anyone help? Is it a bug or is it me?

it sounds like you have another pet selected when you get that error. sometimes when you lose and forget to heal right away, or if your pet drops below the hunger/happiness threshold, they'll disappear from the "battle again" page and it takes a few minutes for them to show back up. what you're doing is how to fix it though, just go back to the challengers page and reselect everything =)

Thanks That makes sense :)