Do you use solution such as load balancing or something like that?
You can also try in file CustomChartData.ashx (placed in c:\inetpub\SolarWinds\Orion\charts) find following line:
strDataUrl = string.Format("{0}://{1}:{2}", builder.Scheme, builder.Host, builder.Port) + strDataUrl;
and replace it for
strDataUrl = string.Format("{0}://{1}:{2}", builder.Scheme, “127.0.0.1”, builder.Port) + strDataUrl;
Note that for this is needed in IIS binding setup allow All Unassigned IP adress.
In the case, that this will not help I would suggest to open support ticket and we will look at it.