I have been reading a lot lately on the Second World War and about soldiers that were held captive for years. So, we're they still being paid whilst held or was there pay cut off completely?
Yes. In fact, Kurt Vonnegut wrote about the back pay he would receive when he was released from Dresden.
"Once home I'll be given twenty-one days recuperation at Atterbury, about $600 back pay and -- get this -- sixty (60) days furlough. "
http://www.lettersofnote.com/2009/11/slaughterhouse-five.html
I recommend you read the whole letter, it has a lot of insight into his life as a POW.
Also they continued to be promoted in accordance to average promotion time. For example General Wainwright the highest ranking American pow was promoted upon release from a temporary 3 star to a four star General.