I have seen this discussed a few times and have researched each one but so far I have not found a solution.  A couple of days ago I upgraded my server from 7..4.2 to 8.0.3 with no errors.  I did have some issues with old themes that used the solpartmenu and have deleted those themes. Admin:Extensions works fine, just not Host:Extensions.  I thought about reinstalling 8.0.3 to see if it fixed the problem but I am concerned that it will cause more problems!

Here is the Event info:

AbsoluteURL:/Default.aspx
DefaultDataProvider:DotNetNuke.Data.SqlDataProvider, DotNetNuke
ExceptionGUID:34cd704b-0e47-42fc-9273-0367bb16605e
AssemblyVersion:8.0.3
PortalId:0
UserId:1
TabId:2725

RawUrl:/Host/Extensions/tabid/2725/portalid/0/Default.aspx

Referrer:http://www.***.***/Host/tabid/7/portalid/0/Default.aspx
UserAgent:Mozilla/5.0 (Windows NT 6.1; WOW64; Trident/7.0; rv:11.0) like Gecko
ExceptionHash:usU4W/5E6p8Z1TyceKy/Tg==
Message:Object reference not set to an instance of an object.
StackTrace:

InnerMessage:Object reference not set to an instance of an object.

InnerStackTrace:
   at DotNetNuke.Services.Installer.Packages.PackageController.CanDeletePackage(PackageInfo package, PortalSettings portalSettings)
   at DotNetNuke.Modules.Admin.Extensions.InstalledExtensions.extensionsGrid_ItemDataBound(Object sender, DataGridItemEventArgs e)
   at System.Web.UI.WebControls.DataGrid.OnItemDataBound(DataGridItemEventArgs e)
   at System.Web.UI.WebControls.DataGrid.CreateItem(Int32 itemIndex, Int32 dataSourceIndex, ListItemType itemType, Boolean dataBind, Object dataItem, DataGridColumn[] columns, TableRowCollection rows, PagedDataSource pagedDataSource)
   at System.Web.UI.WebControls.DataGrid.CreateControlHierarchy(Boolean useDataSource)
   at System.Web.UI.WebControls.BaseDataList.OnDataBinding(EventArgs e)
   at System.Web.UI.WebControls.BaseDataList.DataBind()
   at DotNetNuke.Modules.Admin.Extensions.InstalledExtensions.BindGrid(String packageType, DataGrid grid, Label noResultsLabel)
   at DotNetNuke.Modules.Admin.Extensions.InstalledExtensions.extensionTypeRepeater_ItemDataBound(Object sender, RepeaterItemEventArgs e)
   at System.Web.UI.WebControls.Repeater.OnItemDataBound(RepeaterItemEventArgs e)
   at System.Web.UI.WebControls.Repeater.CreateItem(Int32 itemIndex, ListItemType itemType, Boolean dataBind, Object dataItem)
   at System.Web.UI.WebControls.Repeater.CreateControlHierarchy(Boolean useDataSource)
   at System.Web.UI.WebControls.Repeater.OnDataBinding(EventArgs e)
   at System.Web.UI.WebControls.Repeater.DataBind()
   at DotNetNuke.Modules.Admin.Extensions.InstalledExtensions.BindPackageTypes()
   at DotNetNuke.Modules.Admin.Extensions.InstalledExtensions. (EventArgs e)
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Control.LoadRecursive()
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

A little more info on the previous post.

The URL that clicking the Host Extensions goes to is http://www.xyz.zyx/Default.aspx?tabid=2725 which gives me the error.  However I can change the tabid=2725 to tabid=2747 in the URL of the browser which is the Admin Extensions and all works fine.