Upgrading Drupal

I just upgraded my test drupal install from 4.5 to 4.6 with minimal effort. Now, whenever I try to login, I get (IP substituted):

Fatal error: Duplicate entry 'ea2b42dccc4ec59222fa19b0e7ebad76' for key 1 query: INSERT INTO sessions (sid, uid, hostname, timestamp) VALUES ('ea2b42dccc4ec59222fa19b0e7ebad76', 0, '11.11.111.111', 1114188995) in /home/sites/drupal/includes/database.mysql.inc on line 66

Hello!

-I want to upgrade to 4.6, but I'd like to do a "clean" upgrade, where I keep my content, but do not retain the various modules I've installed previously. In other words, I've got some old stuff in there, and I want to start over. What's the best way to go about this?

Thanks,
Dieter

I re-ran the upgrade script and have a few database edits to do by hand - using phpmyadmin. I don't know anything about SQL or programming so I'm not 100% clear on what the error messages mean & exactly what to do about them!

1: user error: Multiple primary key defined

(from drupal update)
user error: Multiple primary key defined
query: ALTER TABLE term_node ADD PRIMARY KEY (tid,nid)
(from phphmyadmin)
Keyname  	Type  	Cardinality  	Action  	Field
PRIMARY 	PRIMARY 	707  	Edit 	Drop 	tid, nid
nid 	INDEX 	353  	Edit 	Drop 	nid
tid 	INDEX 	117  	Edit 	Drop 	tid
Warning PRIMARY and INDEX keys should not both be set for column `tid`

so it doesn't like both nid and tid being PRIMARY, and i should drop the tid from PRIMARY? I've tried to 'ignore' tid in the edit PRIMARY options, but it doesn't seem to hold the change. It also gives me the error "#1062 - Duplicate entry '218' for key 1 " which seems to mean that all values for nid index are set to 218(?).
Should I delete the PRIMARY key altogether and just make a new one? (if so how do I tell it which table to edit?)

2:user error: Unknown column 'voters' in 'poll'
(from drupal update)
user error: Unknown column 'voters' in 'poll'
query: ALTER TABLE poll CHANGE voters polled longtext
(from phpmyadmin)
Field Type Attributes Null Default Extra
nid int(10) UNSIGNED No 0

Apologies for bringing this back to the top with a new post, but I hoped an updated subject might throw some more light. I'm desperate to jump on the 4.6 bandwagon, but I really need a leg up! I'm proper stuck at the moment - my back-up database is not being recognised by phpmyadmin - 1and1 (hosting support) think it has been corrupted ... so unless that can be sorted out, I cannot get back to square one and try the upgrade again!

The problem:
upgraded from 4.5.2 (fully working) to 4.6.0 as per http://drupal.org/node/20650 instructions. I chose the 'upgrade from 4.5.0' option and it logged OK. I saw the admin page - or rather just the admin log table - there were no top or side bar menus, and therefore no way to get into the site admin pages. The breadcrumb link to Homepage worked, but the same absense of menus left me with only the two node-teasers as content. Htmlsource shows reference to misc/drupal.css but no theme formatting. The content is enclosed within a table, but there's only one table cell on the whole page. The links from node teasers - to taxonomy/term/201, read more, etc - caused error 500.

What is the status of these modules with regard to drupal 4.6?

I do not see them listed in the 4.6 module download section.

My site makes use of these two modules so I can't upgrade until these modules are available.

I noticed the following problem with Drupal 4.6:

UserA creates a page node; If that page is then editted by the Admin, then that page can no longer be editable by UserA even UserA has the "administer node" permission. Even when you click edit at Content List page, it says no access right.