Magento – Bug in CE version 1.9.0.1 connecting via Soap v1

I spent the last two days debugging a problem that caused my site to randomly redirect to the index.php/install page. I solved the problem by clearing the cache and the sessions folder, and then rebooting the server. I found the event that triggered the bug. The problem occurs when I try to add a service reference in MS visual studio 2012 using the following links.

http://magentohost/api/?wsdl 
http://magentohost/api/soap/?wsdl

Using these two URLS cause the following error in the error log.

    [Thu Jul 24 08:20:40 2014] [error] [client 10.0.0.115] PHP Fatal error:  SOAP-ERROR: Parsing WSDL: Couldn't load from 'http://hostname.com/index.php/api/soap/index/?wsdl=1&wsdl%2F_vti_bin%2FListData_svc%2F%24metadata=' : failed to load external entity "http://hostname.com/index.php/api/soap/index/?wsdl=1&wsdl%2F_vti_bin%2FListData_svc%2F%24metadata="\n in /var/www/html/lib/Zend/Soap/Server.php on line 811

[Thu Jul 24 08:20:46 2014] [error] [client 10.0.0.115] PHP Fatal error:  SOAP-ERROR: Parsing WSDL: Couldn't find <definitions> in 'http://hostname.com/index.php/api/soap/index/?wsdl=1&wsdl%2Fmex=' in /var/www/html/lib/Zend/Soap/Server.php on line 811

Here is line 811 of Server.php

$server = new SoapServer($this->_wsdl, $options);

I tried connecting to those URLS on CE version 1.8.0 alpha and they worked fine.

I just recently upgraded from version 1.8.0 alpha to 1.9.0.1.

The following URL doesn't cause a problem in CE version 1.9.0

http://magentohost/api/v2_soap?wsdl=1

Does anyone know if this is a bug in CE version 1.9.0.1 or is it an error in my upgrade?
Can you not connect to soap v1 with visual studio 2012?