Does anybody else get this issue where some message boxes pop up and the tabs disappear? It's impossible to play now because I can't reach the skills tab.
I highly doubt that's the issue; if it was, I would expect it to crop up much earlier in the game. An unsigned (non-negative) 64-bit integer cannot even store one sextillion (1021) which is much smaller than one undecillion (1036).
After some number of page refreshes over a number of days, the game seemed to fix itself. I saved the game from the "Info" tab and removed all browser information (cookies, local storage, etc.) for this domain. After loading that saved game I haven't had any issues.