It's definitly not the latter...reciever dryers don't quite "spill". For something like this, it definitly could be a clogged something...whatever. I assume you hooked up the gauge to the high side since charging is usually done from that side. Depending on what the low side pressure is (higher or lower than normal) that will give a basis as to possible causes.

Essentially, though the only way to figure this one out is to have a professional look at it. If you live near Sacramento, CA, I would gladly check it out for ya for the cost of your gas coming to my school.