Android :: Receiver Save - Not Able To Get IMEI Number Directly

I've developed an application which has a service and boot completed receiver. The boot completed receiver schedules the service to be executed after every 7 minutes. The boot completed receiver saves its context in a public static variable which is then accessed by service whenever it is scheduled by scheduler. The service first gets the IMEI number of phone and then saves it to a file if it is not already saved. Everything worked smoothly but then i logged into market place and after that the scheduled service was not able to get IMEI number directly , neither was it able to open the file which had already been created and it keeps on throwing nullpointer exception for both direct IMEI retrieval and attempt to open file.................