@Sergut
The code in Folders4Gmail is now frames[3] instead of frames[2]. It seems Gmail added an iframe.

Unfortunately, this small change was enough to break the script. :-(

Also, there's a small change because labels are now real links.

I've temporarily uploaded my suggested fix (see comment below) as a userscript:
http://userscripts.org/scripts/show/22660

You can try that until the main script is updated.

@Dannie F 2
Install the script again. The problem with the big attachment icons userstyle should be fixed.

Interesting problem. I guess you had a label named pICS/holidays (ics before "/").

@coder2007
To change the separator character to "-". edit line 537 of the script from
labelName = labelName.replace(/\\/g, "/");
to
labelName = labelName.replace(/-/g, "/");

@Stu
Digging through all my code to help another user? Wow, I'm impressed! Great to have you around.

@daniel
Here's my try. Pretty ugly, but it seems to work:
div.ybaOyc>div>div+div+div+div+div+div+div.ACpQre div.PQmvpb span

With this the spam count is shown again when you are in Spam view. Delete the .ACpQre part, if you don't like this.

The following fix works for me:
Replace (twice)
span[title^="Spam ("]
with
div[id$="^s"] span

The stylish code relies on the id starting with 1f9t. That is not always the case. The id-prefix changes sometimes.

The Folders4Gmail script should look correct now when you use the Gmail Air Skin script. If not, please send me an email.

Thanks for pointing the problem out. It was a small mistake in my script.