Report Viewer fails without indicating error

Conditions:

1. Report specifies list of available string values for a parameter.
2. Report works correctly on report server when selecting multiple values from check box list.
3. In .Net app, report fails to render if concatenated string of values passed to report, e.g, "1,2,3" even with all values in string are listed as available individually but the specific string was not in THE available value list.
4. In the report, values are used only to filter visibility of report sections and not for retrieving data by parsing the string passed, i.e, if "1" in "1,2,3", show section "1."
5. No error or exception occurs either in studio running in debug or on web server running as localhost.
6. Problem was resolved by removing available values from report.  Solution acceptable since report only used in web app.

Much time was wasted tracking problem and resolving as noted.  Does SSRS report viewer log errors or exceptions that might have provided direct path to problem?  Can report viewer process be traced?

Marty G.