First of all - Happy New Year!!!

Now, on to business:

Occasionally, I'll experience a bug that prevents me from reading books by dropping them from my inventory onto my avatar. I'll click the book in my inventory, drop it onto the avatar, and it'll just appear back in my inventory without opening up for my perusal. The only way around it is to drop the book on the ground, then click it (thereby opening it), read what I need to read, then select the "Take" option from the book's corner. This is SERIOUSLY annoying during the Temple's 7-shrine pilgrimage quest.

Next:

Sometimes, the inventory mouseover item popups stop working. I can pick items up, take them out, put them in, mouseover, etc etc... no information popups. On occasion, the problem will fix itself, and the popups will come back after a time. Other times, it has been an indicator of an impending CTD.

Next:

The last couple days, I've gotten random COMODO firewall prompts after an hour or so of gameplay. Apparently, Morrowind wants to connect to the internet. Why?...

I've got MW+BM+TB, MCP 1.9, UMP, MGE 3.8.0, some texture replacers, the Bethesda plugins, but no other content-adders. The mouseover bug used to happen with pure vanilla as well. Anyone have these issues, or know of fixes?

Does this happen to all books, or just The Pilgrim's Path?
It is a well known bug that happens with that book. The Patch Project attempted to fix it, but it still seems to happen (sometimes) even with it.

The mouse glitch, as you suggest, is probably just a sign of an impending crash.

No idea about the Firewall prompts. But make sure you have all other programs closed when playing.

Quite frankly, I'm not sure. I only ever notice it on Pilgrim's Path, as it's the only book I read several times in a short stint. I'm not gnerally, er.... very 'bookie' in my gaming. Next time it happens, I'll try to switch to another book...