[Forum] reply posts not working getting error message

[Brendaleann]

We are having an issue with our members trying to reply to threads. They sometimes get this error message:
Warning: preg_replace() [function.preg-replace]: Compilation failed: lookbehind assertion is not fixed length at offset 176 in [path]/includes/functions_newpost.php on line 278

And sometimes they get their reply in but an empty post box appears from them above their post.

We recently just moved to a new server.

Any help would be appreciated. We are running on 4.0.5

Thanks!

[Brendaleann]

anyone? We've tried the downgrading to 8.20 until they get it fixed if we have PCRE version 8.21 installed on your server. But that didn't work. We have been trying to fix this for the last 2 days and it's very frustrating.