I asked our well-known friend - Mr. Google - about possible solutions of the issue. Searching through the proposals, I found the right one. Since the combination - SQL Server 2005 + MS Vista Business - is not rare (and is expected to show up more and more often in the business world), I decided to post that solution here, with a hope, that this will help others. The original of the article (in German) can be found here:
"It can happen that SQL Server 2005 Reporting Services installed on the Vista-equipped PC will not work after installing MS Vista Service Pack 1. The installation of the Service Pack 1 ran smoothly and error-free, but reports from SSRS are not available anymore.
The symptoms can be:
(1) requests to http://localhost/reports end with error message about failed connection attempt;
(2) requests to http://localhost/reportserver end with an "HTTP 403.1" error message ("Forbidden");
(3) you may find error messages about failed connection attempt to 127.0.0.1:443 in the log files of the Reporting Services, although you don't use HTTPS/SSL;
The solution is easy if you know the reason: the installation of the Service Pack 1 revoked the "Execute script" right of the virtual folder ReportServer. To resolve the issue, do the following:
(1) Start IIS Manager
(2) Navigate to the virtual folder ReportServer (Computer Name->site where SSRS was installed)
(3) Double-click symbol "Handler mappings" in the central part
(4) Select link "Edit feature permissions" in the right part of the screen - "Task area"
(5) Make sure that Read and Script are enabled (Execute is not required). Installation of the Service Pack 1 has disabled Script option)
(6) Click OK
(7) Close IIS Manager
Reporting Services must work immediately afterwards. Restart is not required."
So, I hope this solution will save your time and energy. I will appreciate any feedback.