Update namespace of existing Custom webparts

Hello,

I need to develop on an existing project (SP2010).

Lots of namespaces of webparts are not ok so I have updated them.

Of course when I deploy existing webparts are not working correctly (bad namespaces and assembly name)

I have update the database AllWebParts for changing the assembly name and namespaces.

I am not able for the moment to update the column tp_AllUsersProperties and tp_PerUserProperties

When I try to go to the site I get the following error :

[ArgumentException: The serialized data is invalid.]

Is there an API in Sharepoint for changing the content of this column :

tp_AllUsersProperties and tp_PerUserProperties

I htink it is my last step to do for everything working well

This is the same problem : http://mailarchiver.org/mail/topic/how-can-you-replace-an-old-web-part-a-new-one-11727167

http://zetitle.wordpress.com/2010/08/11/upgrading-webparts-with-new-codebase/

Thank you for your help

Michael