Hi,
this is a problem of your template, in file /templates/gamers/css/bootstrap/bootstrap-default.css at line 5094 you have this:

#member-registration input, #member-registration textarea {

width:86%; 

}

With this all input have 86% of width, this is wrong because it is not true of the various plugins that can be applied to the form of Registration.

Solutions
There are many solutions to fix, I'll suggest two of these

1) In file /templates/gamers/css/bootstrap/bootstrap-default.css replace line 5094,5095,5096 with this:

#member-registration input[type="text"], #member-registration input[type="email"], #member-registration input[type="password"], #member-registration textarea {

width: 86%;

}

2) add this code in some CSS file

#member-registration input[type="checkbox"], #member-registration input[type="radio"], #member-registration input[type="password"]{

width: auto !important;

}