could be, or your second psu could be underpowered? loose system specs would help, old psu watts, new psu watts and brand for both of them, cpu number of hdd and GPU type is all thats really needed, we don't need to know how many webcams you've got plugged in etc. just the basics.
+1, if that 250w was solely a 12v supply it would come out at 21A when the card needs more like 24a (and as 3 and 5 are 115 its more like 11 ). You need to look at good brand names around the 450w mark.