-12V line very low

[Cooler666]

my -12V line is very low: -12.60

i have an Aopen 300W running a P4

my other lines are alright though. Since i connected a 80mm fan to my motherboard it takes longer for Windows at the beginning to power up the USB modem, i.e. i have to wait like 20 seconds everytime i get into Windows to be able to connect to the internet.
Do you think this is a power problem, and do you suggest i get a new PSU?

Thanks