Getting Fettal Error in Plugin

[Rohit]

Today I upgrade forum from 1.6.3 to 1.6.4 but I'm getting following error when I press Plugin Option from Admin Panel:

Fatal error: Cannot redeclare class MyBB in /home/********/public_html/www.****************.com/forum/inc/plugins/class_core.php on line 12

What should I do?

I can check coding which shows following things on Line 12:

class MyBB {

[ranjani]

if you have recently uploaded a plugin file and getting the error after it then delete that file ..

[Rohit]

I didn't upload any file since last upgrade of 1.6.3

[ranjani]

please see this AND follow the suggestion by MattRogowski