Hello
:)

I found an anomalous behavior of the game. Mayhaps a bug.

I'm on my 1st playthrough. I just passed the combat tutorial and entered the Merchant Guild to talk to the leader of the Guilded Claw.
While inside, I interacted with the tree (to heal my party), the dog, the recruiting lady (to check out how to manage my party, which I didn't change) and then with the leader of the Claw on the stairs (and listened to all his dialogue, accepting to work for them). In that order.
After all of that, pressing ESC would not bring the main menu up.
I could enter all other menus (inventory, game guide, journal, etc), interact with everything, leave the area, and quick save (using F5), but could not open the main menu to access the game's options, save or leave the game.
I exited the Merchant's Guild and went back to the streets of the town, tried there, nothing.
Went back into the guild, and nothing.
That is when I discovered that I could not access the menu via a button on the interface, as most games allow one to do, which would've been a good way to bypass any problems with the ESC key.

I opened the inventory once more and fooled around with the Class window (to see the available career paths) while looking for a menu button. Unfortunately I don't remember the order I clicked things in while in this window. But when I closed that, the main menu could be accessed once more by pressing ESC.

That is all.
Except for the last part where I opened the Class menu, all I did I chronicled exactly as I did it, so maybe the bug can be replicated.

I hope this helps.
Best luck.
;)