mylex accele raid (dac 960 error

i am using ACER ALTOS 900K server with MYLEX DAC 960 controller and SEAGATE 2*9.1 GB U2W SCSI HDD.NT SERVER 4.0 with SP4 & ORACLE 7.3 WORK GROUP SERVER. as usual blue screen and i had to reset the server manually and after that raid giving error saying that both the hdd are off line.i used alt+R to enter raid config & made the drives online manually. now the server is up but oracle files are missing. why the drives went off line .