Error updating to 2.5

I just replaced 6.x-2.4 by 6.x-2.5 (after deleting the module's directory).

Running update.php causes the following errors:

The following queries were executed
weblinks module
Update #6110

    Failed: ALTER TABLE {weblinks} ADD `urlhash` CHAR(32) NOT NULL DEFAULT ''
    Failed: ALTER TABLE {weblinks} ADD INDEX urlhash (urlhash)
    Failed: ALTER TABLE {weblinks} ADD INDEX last_checked (last_checked)

Update #6111

    variable_del('weblinks_url')

Update #6112

    No queries

Update #6113

    No queries

Update #6114

    No queries

Update #6115

    Failed: ALTER TABLE {weblinks} DROP weight

Update #6116

    UPDATE {system} SET weight=0 WHERE type='module' AND name='weblinks'

MySQL is 5.0.51b.

Can anybody tell me what has to be done? Thanks!