During battles, if I use the inventory, serching for scrolls or wands, the game unpause, and my party receive damage. It's a bug?

This is not a bug. In single player mode, if you go into your inventory screen while the game is paused, the game will automatically unpause. If you do not want to have this happen, play in the multiplayer mode and use the Serial (Null Modem) option

Huh? Null modem? Of course not, just choose Create game on TCP/IP.

But I knew this was in BG1 but I thought the games stayed on Pause when you go to the inventory in BG2?

I does stay paused when go to your inventory. I had the same thing as Thorr sometimes but I thought it was because I took something out of my bag of holding

indeed but this shouldn't happen in BG2, when going to the inventory the game should still be paused.

I've had that same thing happen typically while I'm trying to quickly dig a ring out of my gem bag. I can't tell you how many times I've waded into a fight wearing my charisma ring when I meant to be wearing my invis-o-ring.

Anyway, I'll get the invis ring sent to backpack and will be dragging it's icon to my hand slot only to notice my portrait quickly filling with red. Not cool.

thinking of getting hurt suddenly, I had this exp duirng BG1. I used the flame sword from ToSC. Whenever I rest, after waking up my character will suffer -5 to hit points... suddenly! I wonder this is because he got burned by the flame sword??!! :P

The game will still be paused when you switch over to your inventory - it just unpauses when you start to replace potions, weapons and stuff like that (and admittedly it seems a bit "strange irl" that you can do hat inmidst of a fight)