Hi!
A couple of days ago I purchased a version of Baldur's Gate II for mac.
It worked perfectly for 4 - 5 days (fast, no crashes, it's a very good version).
This morning I tried to launch the app and it didn't work.
It opens itself in the dock and immediately fade out, giving me no error message.
I don't have any clue.
Did anybody experience a similar problem?
Thanks in advance for any help you can give me.

P.S.

I have a 2012 macbook with Mavericks os.

I had a somewhat similar situation w/ BG1 not long ago. I have a 2009 iMac with 10.8.5 Mountain Lion. Not sure if we're talking apples to apples here, but you might try this:
(I installed GOG downloader & had it on; not sure if it's relevant)
Find appropriate Baldurs Gate disk image on your hard drive & double click it
Window appears with Baldurs Gate icon & Applications icon (large size)
Drag Baldurs Gate to Applications
When that's done, try re-launching BG application

Perhaps the Wine/Wineskin wrapper gets some errors or corruption? This operation seemed to clean up my issues & was much faster than un-installing & re-installing the whole package… There was no loss of Save files or anything

I have the same set up as you do and had the same problem. For whatever reason, vanilla BG1 wouldn't start up after four or five plays, and if it did, was wont to crash when least expected. The only thing that worked was shutting down and then restarting my computer. Why, I don't know.

That being said, I've installed a number of mods and haven't had that problem. Not one crash, not one failed load. Take that for what it's worth.