Huzzah! Yes, always check your cables first.
In college, I was relayed a version of a story about either a CS student taking a test or a job applicant being evaluated (this works for either). His task was to troubleshoot a laser printer. He spent an inordinate amount of time trying to figure it out before finally giving up. The problem? One of the cables was pulled out only just enough to not make a connection, but otherwise looked connected. :/