Possible Duplicate:
Bug: Illustrator now refuses to draw lines with stroke weight below 1 pt
On my Illustrator CS5.5 I have the strange behaviour that when I make a perfect horizontal line, the stroke weight has a minimal value of 1pt. I can set it to 0.5pt, but it will jump back.
If I make a non-horizontal line and set its stroke weight to a value <1pt, everything is OK. The moment I make that line horizontal the weight jumps back to 1pt. It is possible though to set the weight to 0pt, however this renders the line invisible.
Is there a setting I can change to avoid this behaviour or is there some special reason for this?
