It probably means the refresh rate on your monitor was too low, or your monitor just sux0red in general. Next time, demand a digital flat panel.You probably also made the typical mistake of intermediate hax0rs - "intermediate" in terms of how many years you've been computing, not your technical ability. Those of us who've been doing it for many years (17 for me - I started when I was 10) learn that the best practice for coders and other hardcore computer users is to say "fuck what it looks like, 90\% of being productive is using your tools properly anyway" and take *many* short breaks.
I try to work 15 minutes on the computer, followed by 5-15 minutes off, repeat until my day is done. This gives me plenty of time to rest my eyes, stretch my hands, do some paperwork, go to the bathroom, and most importantly zone out and give my neurons a little rest.
When I finally gave up trying to be a hardcore code-until-you-drop guy, and forced myself to Ctrl-C every 15 minutes or so, I found my code got insanely better - I was spending less than half as much time coding, yet I was actually getting things done faster. The amount of time I spent debugging dropped to about a tenth of what I was doing before.
It took me awhile to figure out why that happened, but finally it dawned on me that I was commenting the shit out of everything so that I wouldn't be lost when I went back to writing - and when I was staring at the ceiling twiddling my thumbs, I'd really start thinking about my code's structure rather than the details.
Hope this helps you in your quest to become l33t among the l33t...