Website word changes, please help

hi- i have a problem and was wondering if anyone can help me.

 

i have a 2010 macbook pro with symantec antivurus for mac

 

i think i may have a virus of some sort.. there are two main problems

 

1. my facebook keeps logging off and i am unable to log back on, i am always redirected to the home page

2. on webpages, names and pronouns are changed to the n-word (n****r) and "the"s are changed to "da"s

 

 

please help me, thank you!

http://a4.sphotos.ak.fbcdn.net/hphotos-ak-ash4/418173_2849791082894_1202970293_32506775_882064913_n.jpg