Yes! Its so annoying. >:(
It never happened before on me.

Dont mean to hijack your thread, but since you’ve already opened one and my problem is the same, allow me to share the infection detals message:

http://www.avast.com/lp-fr-virus-alert?p_ext=&utm_campaign=Virus_alert&utm_source=prg_fav_80_0&utm_medium=prg_systray&utm_content=.%2Ffa%2Fen-ww%2Fvirus-alert-default&p_vir=URL:Mal&p_prc=C:\Program%20Files%20(x86)\Mozilla%20Firefox\firefox.exe&p_obj=http://ad.yieldmanager.com/st?ad_type=iframe%26ad_size=160x600%26site=302388%26section_code=ros%26ypos=SKY%26cb=1372708791.788141%26yud=smpv%3D3%26ed%3DzxE1dBLogBKJveCyGLqpeAd3J2gVQhZN8sL6&p_var=.%2Ffa%2Fen-ww%2Fvirus-alert-default&p_pro=0&p_vep=8&p_ves=0&p_lqa=0&p_lsu=24&p_lst=0&p_lex=210&p_lng=en&p_lid=en-ww&p_elm=7&p_vbd=1489