I reinstalled the client, and the problem is still there.
However, Overclockd, I repeat it: the walnut Hills bug is not happening when I'm already in any session: if Walnut Hills comes before I join another G&G map, this NEVER happens: the load is fine and I can play the map always. It's just when I want to join, without having played any previous session. And it makes me have to turn off the whole system, without having played a single second.
This bug happens 90% of the times I join walnut hills, and as there are 4 maps, it's 22'5% times I want to play this mode. And normally, it's the best mode: Suburbination, Gnome bomb etc are always empty.
At this moment, I just ask for a 'Cancel Button' on map loading, because today I tried three times, at different hours (so, not joining the same session), and happened again. And, be sure, I will ALWAYS hit that Cancel button on Walnut Hills. By the way, it's even the worst map on G&G: quite hard to defend by the plants, too easy for the zombies.
And, on the Garden Ops issue, I simply don't play them anymore.
On the other side, the Mega-Flower Map design is awesome. And the bug never happens on that one, neither on the Golf Field or the Cucumber rocket (I'm sorry I don't know the exact names: my client is in spanish).