Database and forum problems!

[umang26]

I had recently moved to a new server and since then, I have been facing problems. Sometimes, when I open certain threads, I see this error.

Warning: Cannot use a scalar value as an array in [path]/includes/class_postbit.php(314) : eval()'d code on line 86

Further down, there's a vBulletin message that says

Unable to add cookies, header already sent.
File: /home/ranglafi/public_html/includes/class_core.php
Line: 4495

This happens to my users too, but sometimes they see this error where I don't and vice-versa. (I see this in the admincp too, when I try to search for users.)
First I thought this was a problem with the vBulletin files. So to confirm, I uploaded the same files on a free host along with the same database and I had the same issue. Then, I uploaded an older database with the same files and saw that everything was fine! So now I know that there was some issue with the database. I tried to repair and optimise it, but it didn't help. I even tried to change the style but I had the same problem again.

Now my best guess is that I need to continue with the old database and ask my users to register again. This will not be good for my website.

So my real question, is there a way to only add the users and their relevant information from the new database to the old one?

Somebody please help, this is urgent.