After restarting the system I tried to check few websites on one of my qubes. None of them worked. It was just loading, but blank screen.
Then used the default disposable, everything opened extremely fast.
Returned to my previous qube (after stopping it and then starting it again), surprisingly everything was okay.
But when I tried to close the disposable, together with the bubble saying that is closing, there was another one with a warning sign saying “dispxxx failed to execute getDate in dom0”.
Pretty much exactly as stated. Seems to be common after upgrades thanks to mismatch between running kernel & qubes-core-agent/qubes-core-qrexec (I “think”). Reboot post-dom0 update will likely sort ya.