Here is a steam discussion I started about the issues and any fixes the community has found so far:
Problems after 17/06/14 update
210 Posts
Posted Jun 19, 2014
Replied
1 hour
later
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174 Posts
Posted Jun 19, 2014
Replied
3 minutes
later
-snip tmast u ninja-
797 Posts
Posted Jun 19, 2014
Replied
38 minutes
later
I see that this is a universal problem now. I am currently using the independent model viewer outside hammer as a reference right now until the fixes are made
193 Posts
Posted Jun 19, 2014
Replied
54 minutes
later
Seems to work again, though I never tested it while it was broke, I just got another 12mb update and everything works as far as I can see.
121 Posts
Posted Jun 19, 2014
Replied
1 minutes
later
Darn it LoneWolf2056 got here first, I was just one my way to tell the news also 
HAMMER AND P2 WORK
193 Posts
Posted Jun 19, 2014
Replied
5 minutes
later
2 days without mapping and we all start going a bit crazy, should be part of, "You know you have been doing too much hammer when" 
232 Posts
Posted Jun 19, 2014
Replied
8 minutes
later
HOOORAY!!!! =D
630 Posts
Posted Jun 19, 2014
Replied
7 minutes
later
Im just copying the models from other maps
45 Posts
Posted Jun 19, 2014
Replied
19 minutes
later
Got the update here too, everything working again, so far
412 Posts
Posted Jun 19, 2014
Replied
27 minutes
later
Yay this update did absolutely nothing for me! (Time to throw myself out the window)
Edit: I now realize this is a 1 story building
973 Posts
Posted Jun 19, 2014
Replied
39 minutes
later
Lol honestly I don't care about the fix update, I fixed mine within 1 day
2,386 Posts
Posted Jun 20, 2014
Replied
9 hours
later
I keep having the same issue: Portal2 refuses to close! No matter what I'm doing, it crashes when I try to leave a workshop map from playing, also when I'm at the main menu and want to quit.... Isn't anyone else experiencing this issue?
1,183 Posts
Posted Jun 20, 2014
Replied
44 minutes
later
josepezdj wrote:
I keep having the same issue: Portal2 refuses to close! No matter what I'm doing, it crashes when I try to leave a workshop map from playing, also when I'm at the main menu and want to quit.... Isn't anyone else experiencing this issue?
Until they fix this problem, write "quit" in the developer console.
2,386 Posts
Posted Jun 20, 2014
Replied
2 hours
later
yishbarr wrote:
josepezdj wrote:I keep having the same issue: Portal2 refuses to close! No matter what I'm doing, it crashes when I try to leave a workshop map from playing, also when I'm at the main menu and want to quit.... Isn't anyone else experiencing this issue?
Until they fix this problem, write "quit" in the developer console.
Damn, Yishbarr! THANK YOU! 
797 Posts
Posted Jun 20, 2014
Replied
5 hours
later
lol, i always did that, it was way faster
2,842 Posts
Posted Jun 20, 2014
Replied
2 hours
later
I always go for "Exit" instead of "Quit"
10 Posts
Posted Jun 26, 2014
Replied
6 days
later
CamBen wrote:
Wait, I managed to fix itSince most of you run off a windows 7/8 now probably, here's a fix for hammer. Replace your Common/Portal 2/Bin/ folder with this:
Is working perfectly now.
Thank you.
174 Posts
Posted Jun 26, 2014
Replied
1 hour
later
But Valve fixed the update.
412 Posts
Posted Jun 26, 2014
Replied
48 minutes
later
Not for me. nothing changed, actually, and I was just coming here to get some help.
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174 Posts
Posted Jun 27, 2014
Replied
11 hours
later
Verify cache.