If you use a Cisco CSS switch for load balancing or content caching to a SharePoint Server farm, you may be unable to edit Office documents correctly if the switch is configured for Layer 5 content rules. By default, the Cisco CSS switch will block certain HTTP methods that are used to establish web authoring, and these can cause a problem for your Office clients and/or any SharePoint development from the client. 

Please see the following post for details:
Unable to Open Office Documents for Edit From SharePoint Behind Cisco CSS Load Balancer