Search "ed/max/min," "ed/min bug," or "ed/max big." Something like if they are used off weapon, the ed% only applies to the non +'ed stat. So a 40/15 max would be +40% min, +15 max.
Jerkazoid - not actually completely true. Only %ed added after +min or +max is bugged. Unfortunately when both are on one jewel the game adds the +min/max first In your example the 40% ed from the first jewel will still apply to max, just not the second jewel.
If you socketed them the other way around, then you would get no %ed max as you listed.
gfattack, 40%ed/15 IAS jewels are not bugged in any way that I am aware of, except as above if you socket one after a jewel with +min/max on it (same for any %ed jewel, even single-mod ones).
rockboy888, the bug does not affect weapons at all.