I have two blogs: dominantforce.wordpress.com and pstrix.wordpress.com. Both use the Modularity Lite theme with no customization or modification.
I have not changed anything or installed anything new on either blog (to my knowledge), yet both blogs are now missing the vertical scroll bar. Both sites had scroll bars before (a month or so ago).
I've been trying to troubleshoot the issue myself, with no success. I found several support articles addressing missing scroll bars, however they all involved modifying/customizing CSS code which as far as I understand will cost me to upgrade, are somewhat beyond my level of CSS comprehension, and I'm not sure they apply to my specific situation.
Blog url: http://dominantforce.wordpress.com/