Did you get a hollow bar or something? I regularly deadlift 350# on my 6 foot standard bar with no problems. And I haven't seen any claims about safety issues elsewhere. If you actually look at the bars, the central section when the maximum loading is is the same diameter on standard and Olympic bars.
I googled up standard barbell weight capacity and most responses on forums and articles say that standards are only rated for ~230 lbs. This one says 300 http://www.building-muscle101.com/weight-lifting-equipment.h... this guy says ~200 http://forum.bodybuilding.com/showthread.php?t=945996&pa...
Here it says 200 for 5ft http://www.bigfitness.com/noname8.html and 250 for 6ft http://www.bigfitness.com/weigbarbr6st1.html
It's a nightmare trying to find out the specs. I prefer a 5ft bar. Say I get more plates and this bar can't handle them, then I have to try other bars. I wish I could sell this weight set and get olympics. No worries about capacities there.