issue never comes up in terminal. sudo apt-get install works fine. must be a software center bug. it happened just after updating this morning...
temporarily solved by changing permissions to software center. now i don't need root to use it.
Samsung Galaxy Precedent (rooted, AreaRom 3.4 , sd-ext w/ 3.65GB internal space)
Kindle Fire (1st Gen, rooted, AOKP JB 4.1, Nova Launcher)
Samsung Galaxy SIII 4G LTE (rooted, Carbon ROM)