Blog Posts Fatal Error

I'm getting the error below when I save a blog post on my local build, and a white screen on my testing server. I'm working on it just to check I haven't messed up the update (I'm a bit of a noob). Any ideas what it could be though?

Thanks

( ! ) Fatal error: Call to a member function return_instance() on a non-object in C:\Users\Mark\Documents\Web Design Local\host\longshot-photo\perch\core\lib\api\PerchAPI_Form.class.php on line 408
Call Stack
#   Time    Memory  Function    Location
1   0.0000  259896  {main}( )   ..\index.php:0
2   0.3340  2692440 include( 'C:\Users\Mark\Documents\Web Design Local\host\longshot-photo\perch\addons\apps\perch_blog\modes\edit.pre.php' )   ..\index.php:26
3   0.3610  4254216 PerchAPI_Form->receive_from_template_fields( )

Diagnostic Report

    Perch: 2.8.2, PHP: 5.5.12, MySQL: mysqlnd 5.0.11-dev - 20120503 - $Id: bf9ad53b11c9a57efdb1057292d73b928b8c5c77 $, with PDO
    Server OS: WINNT, apache2handler
    Installed apps: content (2.8.2), assets (2.8.2), categories (2.8.2), perch_blog (4.5.4), perch_forms (1.8.2), perch_gallery (2.8.5), perch_backup (1.2)
    App runtimes: <?php $apps_list = array( 'content', 'categories', 'perch_gallery', 'perch_blog', 'perch_forms', );
    PERCH_LOGINPATH: /perch
    PERCH_PATH: C:\Users\Mark\Documents\Web Design Local\host\longshot-photo\perch
    PERCH_CORE: C:\Users\Mark\Documents\Web Design Local\host\longshot-photo\perch\core
    PERCH_RESFILEPATH: C:\Users\Mark\Documents\Web Design Local\host\longshot-photo\perch\resources
    Image manipulation: GD
    PHP limits: Max upload 64M, Max POST 3M, Memory: 128M, Total max file upload: 3M
    Resource folder writeable: Yes
    HTTP_HOST: longshot-photo
    DOCUMENT_ROOT: C:/Users/Mark/Documents/Web Design Local/host/longshot-photo
    REQUEST_URI: /perch/core/settings/diagnostics/
    SCRIPT_NAME: /perch/core/settings/diagnostics/index.php