Fatal MySQL error in several pages

URL to your eFiction: http://www.libraryofmoria.com/a/
Version of eFiction: 3.5.3
Have you bridged eFiction, if so with what?: No
Version of PHP: 5.2.17.
Version of MySQL: 4.1.22
Have you searched for your problem: Yes
If so, what terms did you try: SELECT author.penname as penname
State the nature of your problem:

When trying to access Authors I get the following error message:

A fatal MySQL error was encountered.
Query: SELECT author.penname as penname, author.uid as uid, ap.stories FROM fanfiction_authors as author LEFT JOIN fanfiction_authorprefs as ap ON ap.uid = author.uid WHERE ap.stories > 0 GROUP BY author.uid ORDER BY author.penname LIMIT 0,150
Error: ()

When trying to access Submissions I get:

A fatal MySQL error was encountered.
Query: SELECT story.title as storytitle, chapter.uid, chapter.sid, story.catid, chapter.chapid, chapter.inorder, chapter.title, author.penname as penname FROM (fanfiction_chapters as chapter, fanfiction_authors as author) LEFT JOIN fanfiction_stories as story ON story.sid = chapter.sid WHERE chapter.validated = '0' AND chapter.uid = author.uid ORDER BY story.title
Error: ()

When I try to access Members I get:

A fatal MySQL error was encountered.
Query: SELECT author.penname as penname, author.uid as uid, ap.stories FROM fanfiction_authors as author LEFT JOIN fanfiction_authorprefs AS ap ON author.uid = ap.uid GROUP BY author.uid ORDER BY author.penname LIMIT 0,150
Error: ()

When I try to access Admins I get:

A fatal MySQL error was encountered.
Query: SELECT author.penname as penname, author.uid as uid, count(stories.uid) as stories FROM (fanfiction_authorprefs as ap, fanfiction_authors as author) LEFT JOIN fanfiction_stories as stories ON (author.uid = stories.uid) AND stories.validated > 0 WHERE ap.level > 0 AND author.penname LIKE '%' AND ap.uid = author.uid GROUP BY author.uid ORDER BY author.penname LIMIT 0,150
Error: ()

When I try to access Action Log I get:

A fatal MySQL error was encountered.
Query: SELECT DISTINCT log_type FROM fanfiction_log ORDER BY log_type
Error: ()

Do you have a test account for us? Yes ( http://www.libraryofmoria.com/a/viewuser.php?uid=153  PW: test).

We have had 3.5.3 running smoothly for a while. I believe that these errors are linked with changes our provider made to our PHP and MySQL version, which are currently the ones listed above, but used to be as follows:

Version of PHP: 4.4.7
Version of MySQL: 5.0.51

So... any ideas on what we should do? Would reinstall 3.5.3 be enough? Something else?

We really appreciate any help you can lend us.

Best
Talullah