i've had this happening on increasingly frequent occasions this test. it isn't just that clicking inventory items is off, it is a larger 'focus' issue.
keyboard navigation in game (enter, up, down, spacebar) doesn't work when the game has focus (left right does), but instead is stuck in the chat area just like clicking. so the only way to interact with anything in game is to click directly with your mouse and use menus, and you can't do some things at all like climb/get off ladders.
reloading the browser clears the issue, but it comes back often. I haven't pinned it down to anything reproducible yet. thought it had something to do with switching windows / apps away from the window the game is in while idle, but that doesn't seem to be always the case.
I get a lot of blank squares when I open bags. If it's a tool or a food I can use it or eat it but if I want to move something or donate it I'm out of luck. Those can only be done when the complete picture shows. For me that is a VERY rare event.
I've had Eglantine's issue two or three times. Second time I chatted to Online Help and then wrote a bug report about it, and by the time I'd finished it stopped happening. No reload.
Hopefully fixed for next test, it's rather annoying! It also absorbs a lot of keystrokes from the play screen and sends them to Chat - everything except left and right, pretty much.
I’ve also had this issue, but a reload isn’t necessary: just tap the Ctrl key and it comes back. Same with the jumping issue I’ve had before where everything works except jumping. But yes, it’s almost definitely related to switching windows - three of us in my house have had this issue.
I had this issue twice last test and filed a bug report. I didn't realise about the ctrl key fix - thanks for the tip. I use it for other things like my avatar not jumping, or refusing to stop walking etc.