You might notice that certain documents (with file extensions such as .xps, for example) will display in some web browsers but not in others, when they are requested from a DataPower service.
Diagnosing the problem
A packet capture of the traffic between the client and DataPower shows, instead of a single GET, two identical http GET requests by the client that are nearly simultaneous, in the case of some file extensions.
Resolving the problem
Try disabling the TCP Window Scaling (on DataPower's Network Settings WebGUI page), which is enabled by default. The documentation for this setting states:
Enable TCP Window Scaling:
Allows negotiation of window sizes greater than 64KB. This option is enabled by default. Disabling this option might help workaround TCP systems that do not understand or that misinterpret window scaling.