Just ten minutes after I received your mail, I fixed the problem ! Actually, the problem occured not only when I deleted the Category page, but any page in my Wiki ! Here are the related configurations of my wiki: Window XP Professional SP 2 IIS 5.1 MediaWiki: 1.7.1 MySQL: 5.0 I haven't made any changed in MediaWiki except for some configurations in the localsettings.php file. Here is how I got the solution. 1. I checked on the table mw_archive by phpMyAdmin and found the ar_text field's default value is ' ' (Since I could not see any visible characters in that field, I thought it were null string). 2. Then I tried to edit the default value of ar_text in phpMyAdmin. I leaved the "Default" inputbox with nothing to indicate that I wanted its default value to be null string(' '). I pushed the "Save" button but the result page showed me that the SQL query that had been executed was: ALTER TABLE `mw_archive` CHANGE `ar_text` `ar_text` MEDIUMBLOB NOT NULL , in which without the "DEFAULT ' ' " part. 3. After that, I edited ar_text's default value again. This time, I filled the "Default" inputbox with ' '. I Saved it and phpMyAdmin reported an error(Off course there would be an error). It said the following SQL query had been executed unsuccessfully: ALTER TABLE `mw_archive` CHANGE `ar_text` `ar_text` MEDIUMBLOB NOT NULL DEFAULT '''''' . This time, it came out with the "DEFAULT xx" part! 4. Right in the result page that reported the error, I deleted the contents in the "Default" input box and SAVED. The result page came out and said the following SQL query had been executed SUCCESSFULLY: ALTER TABLE `mw_archive` CHANGE `ar_text` `ar_text` MEDIUMBLOB NOT NULL DEFAULT '' with the DEFAULT being set to ' ' exactly! 5. Then the ar_text error disappeared! The same problem existed with the ar_flags field too, so I changed ar_flags's default value to ' ' in the same way. 6. Now, everything goes perfectly all right. That is how I solved the problem I met. However, I'm still not sure why the problem could exist anyway. Is there any error in the MediaWiki installation code? Or other problems? 2006/8/28, Greg Sabino Mullane <greg(a)turnstep.com>om>: