We just updated the Mac Beta installer to include our newest launcher, which could help if you are having issues with the first launch of the client.
You can download it from the same location on the account page:
https://account.guildwars2.com/download
Note: Re-installing will overwrite the existing game, and you will have to download the game content again. Only re-install if you are having trouble with the launcher. If you are able to log into the launcher, then your client is up to date, and re-installing is unlikely help at this time.
This version of the launcher also has better error recovery, so if your problems persist, it may help to let the launcher stay on-screen for a minute or two.