This is the exact issue I've been running into. Literally every single detail, except I'm on a 15" rMBP. Seeing as how I am also running OSX 10.9 I assume thats the culprit.
I am also having this problem and have been frustrated at not only the bug itself but also on finding anyone else who is experiencing the issue as well. Unfortunately, I am also on a rMBP & OSX 10.9 (beta 3).
Update: I logged this bug in the Mac OSX Developer Forums: https://devforums.apple.com/thread/196854 (must be a mac developer to view).
Yes, 10.9 is very, very pre-release software.
We're filing these bugs with Apple as quickly as we find them...
What did you all three expect fom OS X 10.9 at this point?
That's why beta testers are being called upon…
Thanks Chris. In case it helps your efforts, the bug is still happening in the newly release 10.9 beta 4.
Same problem here on Mavericks. Okay, not literally the same thing, it only happens in some text boxes while not others. A notable example is Dust & Scratches: as soon as I open that filter, I get a message saying "Invalid numeric entry. An integer between 1 and 500 is required. Previous value inserted." Even though I've not entered anything yet. It seems like the mere focus of the blinking text cursor deletes the text inside the box.
I can so far only reproduce this when running Dust & Scratches from a simple action. There's also another filter that does it but I don't remember which one. Dust & Scratches doesn't do it when not run from an action... Very strange and annoying!
Mavericks really did screw Photoshop up very very badly didn't it?! It's like using an early Alpha release...
Also, new machines can't be downgraded to Mountain Lion which means there's no solution so far.
The problem started happening a few days ago, coenciding with the recent Creative Cloud app update...
EDIT: Looks like the problem is semi-fixed if I quit the Creative Cloud app (the one in the menu bar). I say semi because it just came back, though it didn't happen for a while after I quit the CC app.
There's also a weird bug definitely related to creative cloud, a white horizontal srtip window at the bottom of the screen appears when the creative cloud menu is open. See screenshot.
A few months later and I am still experiencing this in PS CC under 10.9.2 (iMac 27" late 2009). Even when booting in safe mode without any extensions on I get the weird behaviour. Has everyone else seen any improvement since this thread was started?
If you have weird things happening on text entry in MacOS 10.9 -- turn off the dictation feature (it causes all sorts of problems).