drupal v5 to v6 upgrade

after an installation to v6, I see database mysql errors (below).
I'm trying to upgrade a v5 to v6 using same mysql database.
can anyone help?

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Warning: Unknown column 'serialized' in 'field list' query: SELECT data, created, headers, expire, serialized FROM cache WHERE cid = 'variables' in /home/shreemaa/public_html/drupal-upgrade/includes/database.mysql.inc on line 135

Warning: Unknown column 'serialized' in 'field list' query: UPDATE cache SET data = 'a:280:{s:21:\"update_watchdog_fixed\";b:1;s:13:\"theme_default\";s:10:\"devimandir\";s:13:\"filter_html_1\";i:1;s:12:\"clean_url_ok\";i:1;s:11:\"site_slogan\";s:0:\"\";s:9:\"anonymous\";s:9:\"Anonymous\";s:14:\"site_frontpage\";s:4:\"node\";s:8:\"site_403\";s:9:\"no access\";s:8:\"site_404\";s:9:\"not found\";s:11:\"error_level\";s:1:\"1\";s:14:\"watchdog_clear\";s:7:\"1209600\";s:5:\"cache\";s:1:\"0\";s:19:\"file_directory_path\";s:5:\"files\";s:19:\"file_directory_temp\";s:4:\"/tmp\";s:14:\"file_downloads\";s:1:\"1\";s:22:\"configurable_timezones\";s:1:\"1\";s:17:\"date_format_short\";s:9:\"Y-m-d H:i\";s in /home/shreemaa/public_html/drupal-upgrade/includes/database.mysql.inc on line 135
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