thanks for the quick answers.Yes im aware of all that.. I think in this case.. is what Ondra said... a problem while using a noise limit. Since I find it to be quite random.. for example.. after some tests disabling all my glasses/mirrors on my scene.. i still get wrong noise values... especially assuming that when I use a Time limit instead... the noise values are totally different. About render settings... im using all on default values. as I usually do, unless i've very strong DOF scenes.
If it shows something like .tex/27.IES' then it will not work, you should place that IES file somewhere on desktop, for example, and reapply it.