Sharepoint - unable to open lookup list [error was 0x81020026]

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C#

ASP

SharePoint

Hi I am very new to sharepoint, I recently modified a code for a content type but it did not work so i tried re deploying the original code which worked before but site homepage only displays run time error now but site action and site lists are there and I was able to view them and central administration is working very well. I checked ULS and it displays:

Unable to open Lookup list '{392C8970-319B-437D-8565-3BD0232BBB86}'.[Error was 0x81020026]


System.NullReferenceException: Object reference not set to an instance of an object.
Microsoft.SharePoint.SPSecurity.<>c__DisplayClass4.<RunWithElevatedPrivileges>b__2()
at Microsoft.SharePoint.Utilities.SecurityContext.RunAsProcess(CodeToRunElevated secureCode)
at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(WaitCallback secureCode, Object param)
at Microsoft.SharePoint.SPSecurity.RunWithElevatedPrivileges(CodeToRunElevated secureCode)

PLEASE HELP MASTERS !!! T_T

What I have tried:

I tried resetting and recycling iis no luck.
Getting latest version did not work also.
Application pool is active.