It is not acceptable to have any errors.

If you're running Linux, however, there's a kernel patch available to mark certain address ranges as bad so that you can still use that memory. It's the badram patch, IIRC.

In fact, recent versions of memtest have a display option to show you the exact parameters you should supply to the kernel for that badram option.

I still believe that you should write down the addresses at which your memory has errors and then repeat the test to see if the addresses are the same. If they are, then it's almost definitely the memory's fault. BTW, I find that it's easier to record the badram-style report than the default report, so you might want to change the output to that mode.