Fatal (and non-fatal) errors

Hi there,

I get the following error appear on an otherwise empty white page:

Fatal error: Call to undefined function: str_ireplace() in /home/sites/danmaurice.co.uk/public_html/modules/search_and_replace/search_and_replace.module on line 241

when I search:
Case sensitive: No
Search for: Haileybury
Replace with: H a i l e y b u r y
Function: Search Body and Title Text
Types: Selected All

If I Simply change the Case sensitivity to 'Yes'
I get (after a little wait) a drupal Search and Replace page with:

warning: Wrong parameter count for str_replace() in /home/sites/danmaurice.co.uk/public_html/modules/search_and_replace/search_and_replace.module on line 244.

repeated 216 times in a red backed box

Followed by

0 occurrences found in the following node bodies and titles:

in a green backed box
and no search results listed.

Any ideas?

Cheers
David