IDK, but the first thing I'd do is to replace the CMOS battery and verify the Date & Time is set correctly in the BIOS. IF you don't have the PC on an UPS then I don't recommend Standby mode, and instead 'Hybrid Sleep' where the memory state is written to the drive. Also, in the BIOS there are settings for 'Power Loss' and you can set it to e.g. 'Power Off'
My feeling is you are having issues with brown-outs, black-outs and maybe a bad PSU or connections. However, IF you allows Windows to Automatically perform 'Updates' e.g. in the middle of the night then sure the PC comes out of Standby -- and performs the updates in an 'ON' state.
You also 'could' have a problem with 'Sleep' and it might be worth while to perform a 'test'; powercfg -energy - http://support.microsoft.com/kb/976034