In my job I work on 230 V-dc systems and it is standard for neither line be earth grounded. Thus both the line and neutral float above ground. If I take a voltmeter and measure the voltage from each line to ground and there is no leakage current favouring one side, I will get an exact split reading of 115 V-dc.
It just seems that your neutral has to be floating somehow and is not tied to the earth ground or not connected well.
On the other hand, are you sure you got an electrical shock? I've experienced a sensation similar to a shock once when my elbow rubbed slightly against a metal beam.
