PEBCAK (problem exists between chair and keyboard)
PEBCAK, one of many terms used in Internet chatting, stands for "problem exists between chair and keyboard," meaning it's a problem in user understanding or behavior rather than something wrong with hardware or software. The term is sometimes used by help desk people since it's a common class of problems.
There are several variations, such as PIBKAC (problem is between keyboard and chair). See chat acronyms.