Passwords not working for some users

I have a number of password-protected pages on my site–just using the default password protection setting on the page–and have a user who is unable to access the pages; it simply asks for the password repeatedly. (Example page: http://www.classiccityband.org/membersonly/piccolo/ )

This happens in both Firefox (Windows 7 and Firefox 37.0.2) and IE. A couple of other users have also reported some similar problems.

I am unable to replicate the problem, but am convinced that she is entering the correct password. My guess is that there is some setting on her end that is causing the problem, rather than a problem with the site since most users don’t have a problem. Does anyone have any insight on what might be causing the issue? Her browser is configured to accept cookies, including third-party cookies.

My site details: WordPress 4.2.2 running Customizr theme; plugins: Akismet, All-in-One Event Calendar by Time.ly, Conditional CAPTCHA, Contact Form by BestWebSoft, Jetpack, and TablePress.

Thanks!