Ok, move your opened bag screen NEXT to the inventory screen => now try drag&drop into a slot <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" /> - the bag screen tends to hide behind the inventory - that's why you think, you can't put anything into it. Same for charm items, BTW.
can this screenie help you?
small +2 res.
medium +4 res.
Large +6 res.
larger +8 res.
very large +12 res.
You can see it in your stats when you drag+drop => resistances change. Sadly no ethereal crystals exist. The German version has tool tips, telling which crystal it is and so you can watch your resistance grow:
fire, water, earth, air, poison, spiritual, shadow bone.