My wife had the same problem with Pug. When we looked at the chat log, she actually was "attacking" but it said that her attack didn't connect, but was really worded weirdly, and the text was blue, like that of You can't perform this action at this time... And it was happening about 90% of the time for her, she couldn't level at all.
On a side note, not sure what the crazy symbol is to the left of your first ability, but if you hit that, your attack is disabled for about 10 seconds, and greyed out. Then it takes forever once it comes back before you can attack again (I kept clicking attach and nothing would happen, if I wasn't partied, I would have died).
I played with that for a while, and never found a use for it... We assumed it would cause your next attack to be stronger, but no, it was actually weaker each time... go fig.