symds.sys and/or symefa.sys causing blue screen of death

My computer has experienced random rebooting and BSOD with STOP: 0x00000050 and indicating problems with either symefa.sys and now lately symds.sys As far as I understand these files has to do with NIS. I have NIS version 17.0.1.19 running on a Win XP Pro, service pack 3, fully updated. I’m getting really confused by this and wonder if NIS has something to with it and, if so, how to get the problem solved. Best regards, Joakim