New build boots fine, runs fine, but recently got a no signal

[espillion]

Hello, recently built a pc yesterday everything was fine after overnight leave on i wakeup and its still fine, but after about 3 hours, the hdtv said " no signal " with a hdmi, also dested a vga and said no signal so i restarted the machine and now there is a signal, what could be wrong?

 

[espillion]

gpu is 550ti

cpu Intel 3rd Generation Core i5-3570K CPU (4 x 3.40GHz, Ivy Bridge, Socket 1155, 6Mb L3 Cache, Intel Turbo Boost Technology 2.0)"

mobo MSI Z77A-GD55 Motherboard (Intel Core i3/i5/i7/Pentium/Celeron, Intel Z77, ATX, RAID, Gigabit LAN, Socket LGA1155)

ram Crucial Ballistix BLS2CP4G3D1609DS1S00CEU 8GB (4GB x2) DDR3 Memory Kit

psu Powercool Modular 750W 80+ Dual 12V V2.2 High Efficiency PSU

hdd Seagate 1TB 3.5 inch 7200RPM 64MB Cache SATA3 Hard Drive

and my television is some random one from sainsburys

 

[espillion]

i asked a friend...and the problem could of very well been a power saving problem of turning the display off after 15 minutes