I just cancelled this eticket, and rebooked the same after visiting a PRS counter. To my utter dismay, I was allotted the same C2/48 WS once again!!
This means that there is something wrong with the seat database of IR reservation systems itself for 12639/40 EXP, and not with IRCTC....
This is something new at least for me. Can anyone share similar experiences on this, please?