Report Server Reports Hanging
To see how long a report takes to load, and what stage is taking up the time use this in SSMS:

USE ReportServer  
SELECT * FROM ExecutionLog3 ORDER BY TimeStart DESC


This will show you a log of the activity for each report being used.
you will be able to see start time, end time (and calculate time taken), which parameters are being used, and the time taken for each of the stages of report loading (TimeDataRetrieval, TimeProcessing, TimeRendering) in milliseconds. Further details relating to the query here

Use this link to troubleshoot each stage, as per your findings