[Mediawiki-l] problem with mediawiki

[wiki software]

hi,
   I had installed Mediawiki 1.7.1 and 1.9.1 locally on the system using IIS
5, PHP5.1.6, and MYSQL server 5.0.24.

It was woking fine for almost week after installaton, but suddenly i get
this particular error message when i try to access the wiki site on my
system.

Wiki has a problem

*Sorry! This site is experiencing technical difficulties.*

Try waiting a few minutes and reloading.

(Can't contact the database server: Access denied for user
'wikiuser'@'localhost' (using password: YES) (localhost))


I have no clue why this is happening though, can someone kindly help me.

Thanks.