Computer restarts randomly

hi just upgraded to an r9 270 dula x rescently i havnt had many problems but I have had to random restarts mainly when just carrying out normal activities and not playing on games. This time i was watching you tube videos then the screen locked up a crazy buzz sound came out from the sound and the computer restarted. I've had a look in the event log and theres loads of ati error messages. Heres a few ive copied and pasted around the time it happend.

0000000018: 2014-03-19 19:51:19:808 Exception: No value exists with that name.
Exception Called by: ATI.ACE.LOG.Foundation.Private.Settings:eleteSetting processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameLOG.Foundation.Private, Version=4.5.5167.40621, Culture=neutral, PublicKeyToken=90ba9c70f846762e)
************************************************************************************************************************

0000000016: 2014-03-19 19:51:19:788 GetTargetTemperatureInfo for (UDID = PCI_VEN_1002&DEV_6811&SUBSYS_E271174B&REV_00_4&10698843&0&0008A) returned : -1
Error Called by: ATI.ACE.CLI.Aspect.OverDrive5.Graphics.Runtime.RT_OverDrive5::Check processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameCLI.Combined.Graphics.Aspects2.Runtime, Version=4.5.5167.40645, Culture=neutral, PublicKeyToken=null)
------------------------------------------------------------------------------------------------------------------------

0000000017: 2014-03-19 19:51:19:788 GetMaxFanSpeedInfo for (UDID = PCI_VEN_1002&DEV_6811&SUBSYS_E271174B&REV_00_4&10698843&0&0008A) returned : -1
Error Called by: ATI.ACE.CLI.Aspect.OverDrive5.Graphics.Runtime.RT_OverDrive5::Check processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameCLI.Combined.Graphics.Aspects2.Runtime, Version=4.5.5167.40645, Culture=neutral, PublicKeyToken=null)
------------------------------------------------------------------------------------------------------------------------
0000000024: 2014-03-19 19:51:19:808 Exception: No value exists with that name.
Exception Called by: ATI.ACE.LOG.Foundation.Private.Settings:eleteSetting processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameLOG.Foundation.Private, Version=4.5.5167.40621, Culture=neutral, PublicKeyToken=90ba9c70f846762e)
************************************************************************************************************************

0000000025: 2014-03-19 19:51:19:808 Exception: No value exists with that name.
Exception Called by: ATI.ACE.LOG.Foundation.Private.Settings:eleteSetting processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameLOG.Foundation.Private, Version=4.5.5167.40621, Culture=neutral, PublicKeyToken=90ba9c70f846762e)
************************************************************************************************************************

0000000023: 2014-03-19 19:51:19:808 Exception: No value exists with that name.
Exception Called by: ATI.ACE.LOG.Foundation.Private.Settings:eleteSetting processID:00916 threadIDCCCThreadNew:Runtime) domainNameCCC.exe ) assemblyNameLOG.Foundation.Private, Version=4.5.5167.40621, Culture=neutral, PublicKeyToken=90ba9c70f846762e)
************************************************************************************************************************