Do you use PHP 5.2.x?
If so, you can enable mbstring extension
I recommend to use PHP 5.3.x with MantisBT 1.2.x

Yes it is 5.2.

Is mbstring turned on by default in 5.3?

What other issues might I find if I stay with 5.2? I actually have read some threads recommending against using 5.3 for other reasons.

@atrol,

This was introduced in 1.2.9 (0013280, 5835572fde9df4d0837f0105c6c44c75fe64c07c).

Unfortunately, I can't think of any alternative way of implementing that fix without relying on mb_internal_encoding().

Therefore, unless you or someone else can think of something, maybe we should just document that enabling mbstring is recommended (and required for logging queries) in http://www.mantisbt.org/docs/master-1.2.x/en/administration_guide.html#ADMIN.INSTALL.REQUIREMENTS ?

Admin guide updated.

In response to 0015575:0035399

Is mbstring turned on by default in 5.3?
no, it depends on configuration, see
http://www.php.net/manual/en/mbstring.installation.php

I actually have read some threads recommending against using 5.3 for other
reasons.
I am not aware that there are issues if you are using PHP version >= 5.3.3
Can you provide links with issues when using PHP 5.3?

In response to 0015575:0035407
Sorry, I have also no idea of any alternative way and no time for further investigation.

What about adding also additional checks to admin/check.php ?
Something like:
print_test_row( 'Checking if extension mbstring is loaded for database query logging', extension_loaded('mbstring') || OFF == config_get_global( 'show_queries_list' ) );
print_test_warn_row( 'Checking if extension mbstring is loaded for better performance', extension_loaded('mbstring') );

David removed the library in next
https://github.com/mantisbt/mantisbt/commit/beb4c5b8381c0f0eca99de23e1021fcebdc51c7a
Paul also in master-2.0
https://github.com/mantisbt/mantisbt/commit/6a165ba57e4b8d683e26f2034b4534af0870c5f2

Marking as 'acknowledged' not resolved/closed to track that change gets ported to master-2.0.x branch