Dell V525W Magenta stops

After I print a one page doc in Microsoft Works, that has ONE LINE of Red printing in it. My Dell V525W stops printing magenta ink. No matter what screen or program I print from, It doesn't even print magenta when I do a print align. The only way to get it back to printing magenta is to go and buy a NEW cartridge. This is the second time this has happened in the last two months. Any ideas why. The v525w shows I still have 87% of magenta left.