So this is quite a common bug. I recieve an invite from a friend. Often, when I accept it, the spinning globe shows up but nothing happens, resulting in a "Sorry we experienced difficulty creating game" error message. The game ususally starts when I invite back, though.

Anyone else seen this happen before?

Me and my friends also have this problem, this and a lot more.
I saw a friend play yesterday, and I was like .. WOW worms on facebook, and I started to play.
Then I was realy dissapointed, when friends wanted to accept my invites they couldn't, if they click on the invite they would get a white page, the problem is sloved if they accesed the game from the "Search for people, places ......" line. A minor Inconvenience.
Then I leveled, did quests, customized worms and island, bought wepons, and after a while I exited the game. When I entered again almoust all my customization, quests and weapons were gone, the game didn't save (it passed some time). Then I read that it can be solved if you acces the inventory before I exit .... another minor inconvenience.
Then I was a bit dissapointed because of limited content, few weapons, few quests and few scens, this is no major thing, I know the game is just at it's begining.
The major problem I encountered was when me and my friends sent gifts to eachother, and we never received them, or at least we didn't receive them in few hours.
And last the most important problem we encountered was when we wanted to battle eachother. It only workes once in a while, usualy we just get "Sorry we experienced difficulty creating game." For example before I wrote this we tried to play and it worked 1 out of 10 times, and I also tried "Battle random oponent online" and it's the same thing.
So ... I don't know if this is browser related but I doubt it, I use FireFox 18.0.2