Standby Wakeup Issue

Hi, I am having a problem regarding waking up from standby mode, after going to standby I have to press a key to wake up either from my mouse or keyboard...sometimes when I press a button to wake up my computer will not wake:? It will switch on and the light will go from blue (on) to orange (standby) about 4-6 times and then it will stay on orange (standby) and I will not get anything on the screen and have to force shutdown by holding the power button:/ When I restart it will say resuming Windows (I do not go into hybernate mode tho) and take a little time to load me back to the loggin screen. This has been happening since I have upgraded my RAM by installing 2GB more into my system... I had also upgraded my graphics card but did not have any problems...I have this problem more if I have my USB TV Tuner card pluged in so I tend to have it unplugged most of the time:/ I am thinking could it be my PSU? I have a 300W standard and having 4 RAM modules and a graphics card (ATI Radeon HD 4650) plus fans etc... I can play games like AVP and GTA IV with no problems so could it be power drain:? NOTE: The first time I had a BSoD when waking up nbut have not had it since.

Thanks in advanced for the help:)

Thanks for the help, It is my PSU as Iv taken my graphics card out and am now using my on board one and not had this problem. I will get a better PSU and reinstall it as soon as... do you know of any brands I should look out for?