hairline in photoshop 7

i am useing photshop 7 and a number of 3rd party plugins to manipulate photo images at 1200 dpi.On occation ,when i have done a fair amount of curve adjustment,when i output to photo paper useind a dell AOI model A920 printer,cyan or magenta hairlines can be seen at the edges of some of the color transitions,I have used a blur of 2.5 pix to try to eleminate it,with no luck.Can anyone tell me where to look to fix this problem.