MVC3 project has Ajax calls failed after deploying to IIS7.5 - visual-studio-2010

Question

I have read almost all of the questions on this, but found no solution. The error I got is 500 Internal Service Error which points to a specific error: CS0103: The name 'ViewBag' does not exist in the current context.
The strange thing is this error only occurs when an ajax call is made. When there is no ajax call involved, the same cshtml page works fine.
Here are the two responses with one that works(first) and the other fails(second):
Request Method:GET
Status Code:200 OK
Request Headersview source
Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8,zh-CN;q=0.6,zh;q=0.4
Cache-Control:no-cache
Connection:keep-alive
Host:localhost
Pragma:no-cache
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36
Response Headersview source
Access-Control-Allow-Origin:Access-Control-Allow-Origin
Cache-Control:private
Content-Encoding:gzip
Content-Length:7033
Content-Type:text/html; charset=utf-8
Date:Mon, 10 Feb 2014 19:25:49 GMT
Server:Microsoft-IIS/7.5
Vary:Accept-Encoding
X-AspNet-Version:4.0.30319
X-AspNetMvc-Version:3.0
Request Method:GET
Status Code:500 Internal Server Error
Request Headersview source
Accept:application/json, text/javascript, */*; q=0.01
Accept-Encoding:gzip,deflate,sdch
Accept-Language:en-US,en;q=0.8,zh-CN;q=0.6,zh;q=0.4
Cache-Control:no-cache
Connection:keep-alive
Host:localhost
Pragma:no-cache
User-Agent:Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36
X-Requested-With:XMLHttpRequest
Query String Parametersview sourceview URL encoded
quarter:1
year:1
Response Headersview source
Access-Control-Allow-Origin:Access-Control-Allow-Origin
Cache-Control:private
Content-Length:48466
Content-Type:text/html; charset=utf-8
Date:Mon, 10 Feb 2014 19:28:29 GMT
Server:Microsoft-IIS/7.5
X-AspNet-Version:4.0.30319
Please help!