I recently built a new computer for the first time using the same parts as the 500 dollar march system builder that they built on this site. When I have the HD 6850 installed, most applications crash the computer. I have tried many different driver versions but none seem to work. Also the cheap geforce 210 that I bought to troubleshoot works perfectly.
that is quite strange. I would also think that a 380W psu is way underpowered, but if it did work for them then it should for you. The case seems fine also, but I would personally add all of the fans that I could to make the GPU as cool as possible. If it is a sapphire card you're using, I've found that their reliability is top-notch. I would call sapphire up, and check with them and see if you've left out somthing critical (no offence) I would check that all of the drivers are up to date but other than that, sorry I couldn't be of help.