500 Internal Server Error (i know, again!)

version 3.2.2 has been running just fine for me for a long time. All of a sudden, I lost my ability to log in to the program at all, receiving a 500 Internal Server error. I re-installed php list, using the 3.2.4 version, upgraded php on my host to 5.6, made sure that magic quotes is on (even though it seems irrelevant now) ,checked all of thep ermissions on ALL the foldersand files (755 or 644). Still no luck accessing the phplist administration. Nothing on my server error log seems to relate to anything in php list. any ideas?