When we have a problem in Dynamics CRM instance of a client, Microsoft has available an online page that we use to do some screening of what may be happening to the instance.
For that we must go to the following URL: https://<OrganizationName>/tools/diagnostics/diag.aspx (change the with the client organization) and from there we will have a page with some information that will be analyzed after we press the Run button.
For example https://myorg.crm4.dynamics.com/tools/diagnostics/diag.aspx
From the Results, we can analyze the Latency, Bandwith, Browser Info and much more.
Hope this helps.
World of an IT guy 