Invision Power Board Problems

[doh85]

When i go to start a new topic i get this:

[code]
Fatal error: Call to undefined function: show_form() in /home/dohdesi/public_html/forum/sources/Post.php on line 418
[/code]

and on line 418 is
[code]$post_functions->show_form(&$this);[/code]

and then when i want to reply to a topic it says

[code]
Parse error: syntax error, unexpected ';', expecting T_OLD_FUNCTION or T_FUNCTION or T_VAR or '}' in /home/dohdesi/public_html/forum/sources/lib/post_reply_post.php on line 910
[/code]

and on line 910 it says

[code]?>[/code]

What should i do to resolve the problem?

Would aprreciate any help!