Akismet – Comments not working (Opera, IE, Safari no, but Firefox & Chrome ok)

Hi,
I am using Luxury theme by Cudazi (latest version) and have realised that comments cannot be posted to the blog or to the guestbook page of my site IF it is viewed in Opera / IE or Safari. Everything works fine in Firefox and Chrome.
The comment box is shown, however when the form is filled out and comment is ‘posted’ in Opera/IE/Safari nothing happens. The message becomes blank but there is no comment on the page. The comment also does not show up in the back end.
I uploaded a clean version of comments.php and that did nothing.
I have turned all plugins off, and then gone through them – and the one that seems to be causing the issue is Akismet.
If I do not have Akismet activated is this going to mean I’ll be bombarded with spam? I have to approve all comments, so nothing will be posted without my okay.. but i’m still concerned about this.
Is there an alternative to Akismet? Thanks, Polly