One day my website domain provider decide to cancel the domain service to my site. Now that I have sort out the problem and reassign the domain to my website, this happen. Now, my site unable to load all the modules. Here is the exception error message:

ModuleId: 486
ModuleDefId: 92
FriendlyName: this month...
ModuleControlSource: DesktopModules/Announcements/Announcements.ascx
AssemblyVersion: 04.03.06
PortalID: 0
PortalName:
UserID: -1
UserName:
ActiveTabID: 36
ActiveTabName: Home
RawURL: /Default.aspx
AbsoluteURL: /Default.aspx
AbsoluteURLReferrer:
UserAgent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.1) Gecko/20061204 Firefox/2.0.0.1
DefaultDataProvider: DotNetNuke.Data.SqlDataProvider, DotNetNuke.SqlDataProvider
ExceptionGUID: e48ca2b2-b37b-4226-b49b-19618c29fca2
InnerException: The type initializer for 'DotNetNuke.Modules.Announcements.DataProvider' threw an exception.
FileName:
FileLineNumber: 0
FileColumnNumber: 0
Method: System.Security.CodeAccessSecurityEngine.Check
StackTrace:
Message: DotNetNuke.Services.Exceptions.ModuleLoadException: The type initializer for 'DotNetNuke.Modules.Announcements.DataProvider' threw an exception. ---> System.TypeInitializationException: The type initializer for 'DotNetNuke.Modules.Announcements.DataProvider' threw an exception. ---> System.Security.SecurityException: Request for the permission of type 'System.Security.Permissions.FileIOPermission, mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' failed. at System.Security.CodeAccessSecurityEngine.Check(Object demand, StackCrawlMark& stackMark, Boolean isPermSet) at System.Security.CodeAccessPermission.Demand() at System.IO.Path.GetFullPath(String path) at System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath, Boolean& pathTooLong) at System.Web.Util.FileUtil.IsSuspiciousPhysicalPath(String physicalPath) at System.Web.CachedPathData.GetConfigPathData(String configPath) at System.Web.CachedPathData.GetConfigPathData(String configPath) at System.Web.Configuration.WebConfigurationManager.GetWebApplicationSection(String sectionName) at DotNetNuke.Framework.Providers.ProviderConfiguration.GetProviderConfiguration(String strProvider) at DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, String ObjectProviderName, String ObjectNamespace, String ObjectAssemblyName, Boolean UseCache) at DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, String ObjectNamespace, String ObjectAssemblyName) at DotNetNuke.Modules.Announcements.DataProvider.CreateProvider() at DotNetNuke.Modules.Announcements.DataProvider..cctor() The action that failed was: Demand The type of the first permission that failed was: System.Security.Permissions.FileIOPermission The Zone of the assembly that failed was: MyComputer --- End of inner exception stack trace --- at DotNetNuke.Modules.Announcements.AnnouncementsController.GetAnnouncements(Int32 ModuleId, DateTime StartDate, DateTime EndDate) at DotNetNuke.Modules.Announcements.Announcements.Page_Load(Object sender, EventArgs e) --- End of inner exception stack trace ---

Can someone please let me know how to restore the site back to its original state? This is urgent.

Make sure you set both connectionStrings in the web.config.  You need to set it in the ConnectionString section and the appSetting section.  The core uses the connectionString setting, but most 3rd party module still use appSetting connectionString (including the core modules).