According to an Internetnews.com article this morning a study released today by security vendor Cenzic Firefox accounts for 44% of all browser vulnerabilities for January through June 2009. Safari (Apple) is second at 35% and Internet Explorer (Microsoft) is third at 15%. If you follow the space this will not come as a surprise. My advice would not be to recommend changing back to Internet Explorer if you use Firefox or Safari and like it. The advice would be to minimize the add-ons you use and always run the updater when prompted to do so.
If you are interested in learning about issues like this as they emerge, sign up for our alerts.