I had trouble upgrading from 4.9.4 to 5.1.2  - in the upgrade log it would say:

00:00:00.046 - Upgrading to Version: 05.01.02 00:00:00.375 - Executing Script: 05.00.00.SqlDataProvider Error! (see 05.00.00.log for more information) 00:00:06.593 - Executing Script: 05.00.01.SqlDataProvider Error! (see 05.00.01.log for more information)

00:00:07.671 - Executing Script: 05.01.00.SqlDataProvider Error! (see 05.01.00.log for more information)

00:00:10.468 - Executing Script: 05.01.01.SqlDataProvider Error! (see 05.01.01.log for more information)

00:00:11.375 - Executing Script: 05.01.02.SqlDataProvider Error! (see 05.01.02.log for more information)

I went and checked the log to see what it said (in the dnn folder - providers/database or something like that) the log would say:

System.Data.SqlClient.SqlException: Cannot find the object 'NTForums_GetForumsByGroup2', because it does not exist or you do not have permission.

and then there would be the same line repeated over and over about granting and revoke rights on sys admin or something.

Anyways, I went and looked at the stored procedures in the database and sure enough, all the way at the bottom was a stored procedure with a qualifier in front of it that made it sort all the way at the bottom - even though i do not use qualifyers. The sp was called exactly what the error said - NTForums_GetForumsByGroup2 - except with a qualifyer in front. No idea what it was doing there. Deleted it and then instalation went smoothly - though I am having trouble with the login - maybe skin related.

Also, when I did the upgrade that had the error in it, it also had an error with the html module - so when I went to the site after the upgrade, all the modules that were html modules were throwing errors. Deleting the NTForums_GetForumsByGroup2 sp also made it so when it did the upgrade the html module did not error.

Hope this helps!

I had the same upgrade error and ran the clean up script which executed ok. I then tried to update from DNN 4.8.2 to 5.1.2 and it seemed to go ok except now I end up at the "Click here to access your portal" and it now seems to be in an endless loop. Every time I access the site it shows this. I click the access link and it just goes through the upgrade process again. anyone know how to get back into the site? I did once use the Active Forums 3 module but have since removed it. Maybe something else is causing this.

Steve

Upgrading DotNetNuke

Current Assembly Version: 05.01.02

Current Database Version: 05.01.00

Upgrade Status Report

00:00:00.046 - Upgrading to Version: 05.01.02
00:00:00.093 -   Executing Application Upgrades: 05.01.01 Success
00:00:00.171 -   Executing Application Upgrades: 05.01.02 Success
00:00:00.171 -   Cleaning Up Files: 05.01.01 Success
00:00:00.171 -   Cleaning Up Files: 05.01.02 Success
00:00:00.171 -   Updating Config Files: 05.01.01 Success
00:00:00.171 -   Updating Config Files: 05.01.02 Success
00:00:00.171 - Performing General Upgrades
00:00:00.734 - Installing Optional Modules:
00:00:00.734 - Installing Optional Skins:
00:00:00.734 - Installing Optional Containers:
00:00:00.734 - Installing Optional Languages:
00:00:00.734 - Installing Optional Providers:
00:00:00.734 - Installing Optional AuthSystems:
00:00:00.734 - Installing Optional Packages:
 

Upgrade Complete

Click Here To Access Your Portal

Steve-
For future reference when upgrading DNN sites:  
Based on forums feedback (as researched by Will Strohl), a jump directly from 4.8.x to 5.x is not recommended.  You should first upgrade to 4.9.x before going up to 5.x. See the recommended upgrade path here:

  http://www.willstrohl.com/Blog/tabid/66/EntryId/102/Suggested-DotNetNuke-Site-Upgrade-Path-s.aspx

 
Sorry I have to tips to offer regarding your immediate "how do I get back to my site?" problem other than to revert to your most recent site backup.  
 
Good luck!
-mamlin