eval error in Firefox 1.0.4 , not in 1.0 and IE

Hello,

i got a javascript error: "function eval must be called directly, and
not by way of a function of another name."
in my website (www.cvotemse.be).

str="a=1;";
eval(a);

The problem is the eval function, but in older firefox versions and IE
it works fine.

Who can help me?

thanks

Pascal