Helvetica font rendering issue on MacBook Leopard
You may have a problem with your font caches. Download a copy of the free Onyx for Leopard, and execute a maintenance/cleaning task for Fonts:



It is recommended that you restart your computer after that. Take the time to see the other maintenance/cleaning options around. It's good to use Onyx every now and then to start from scratch. I use Cocktail which is essentially the same (but paid). I use it probably 4 times a year, but it helps keeping things clean.

Mac OS X doesn't really need these utilities to work, because it does have its own cleaning scripts and jobs, but after so many years of OS X experience, I've noted that some things can escape (or get corrupted) and these small utilities (either one) will save you some time.