Whenever I have certain syntax errors in SQL*Plus on one of my Linux Oracle databases, instead of giving me the error, it just sits there until I kill the process from outside of SQL*Plus. Pressing Ctrl+c doesn't work, and Ctrl+z only works when I'm using rlwrap (readline wrapper). I have waited 20+ minutes on an error message before with nothing happening. If I do something like misspell select, it catches the error just fine, but if I misspell a table or column, put my order by clause before the where clause or try to bring a tablespace online before the file is finished copying, then it hangs.
I checked the alert_log and it makes no mention of anything happening at all. It doesn't matter what server I run SQL*Plus from, it always happens when I connect to this server, and it doesn't happen with any other servers, even if the session starts from the problem server. It even works with another database on the problem machine. I am at a loss for how to debug this. I'm hoping this isn't evidence of my third broken database of the day.