Problem after changing to Rails 2.2.2

Hi,   Yesterday we started migrating our project to Rails 2.2.2. For one of the Ajax Request I faced some problem.   When I click an AJAX link, then in the UI I can see my rhtml code directly like

<% __in_erb_template=true %> <%= render :partial => "manage_availability"%>

And in the console I got this.

Host: harish.example.com:3009

User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-GB; rv:1.8.1.3) Gecko/20070309 Firefox/2.0.0.3

Accept: text/javascript, text/html, application/xml, text/xml, */*

Accept-Language: en-gb,en;q=0.5

Accept-Encoding: gzip,deflate

Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7

Keep-Alive: 300

Connection: keep-alive

X-Requested-With: XMLHttpRequest

X-Prototype-Version: 1.6.0.3

Content-Type: application/x-www-form-urlencoded; charset=UTF-8

Referer: http://harish.example.com:3009/properties/new_property/2

Content-Length: 0

Cookie: __utma=28395323.210196984.1226473975.1226473975.1226473975.1; __utmz=28395323.1226473975.1.1.utmccn=(direct)|utmcsr=(direct)|utmcmd=(none); _vakobi_session_id=0739e0f2aaf155d9a1dd1351ac62f23c

Pragma: no-cache

Cache-Control: no-cache

After this my total server is gone. That time I am getting "500 Internal Server Error".

/!\ FAILSAFE /!\ Sat Dec 27 15:49:47 +0530 2008   Status: 500 Internal Server Error   Invalid new_session option:

Did any one faced this problem? What kind of issue is this? Why the server is going?

After this my total server is gone. That time I am getting "500 Internal Server Error".

/!\ FAILSAFE /!\ Sat Dec 27 15:49:47 +0530 2008 Status: 500 Internal Server Error Invalid new_session option:

The interesting bit are the lines following this. Follow the
stacktrace until it meets your own code and you might be able to
workout what's happening.

Fred