[NextGen Gallery] Upgrade problem

Hi guys,
I’m the editor of https://www.zerogradinord.net and I’m using NextGen Gallery 0.98 and WordPress 2.7. When I try to upgrade the plugin (the operation seems to end without any problem) all the pictures in my post are replaced by a white thumbnail with a red X inside, like the image is missing.
I try with all the new version of NextGen Gallery released in the last months, but I’ve all the time the same problem.
Someone can help me?

This is the thing that I found in MySql overview page:

Colation: utf8_general_ci
Language: Italian
Font: 82%

MySQL
Server: 62.149.150.79 via TCP/IP
Versione MySQL: 5.0.68-log
Set di caratteri MySQL: UTF-8 Unicode (utf8)

Spazio Utilizzato:
Sql204869_1 : 57 MB
Sql204869_2 : 0 MB
Sql204869_3 : 0 MB
Sql204869_4 : 0 MB
Sql204869_5 : 0 MB
TOTALE: 57 MB * * arrotondato al megabyte piu’ vicino

Spazio acquistato:500MB

If you need more information about it, I can search for you.
Many thanks.

MM