cannot activate plugin

Each time I try to, I get the error: The plugin does not have a valid header.

Any ideas? I disabled my old calendar plugin.

I'm using Buddypress 1.5.1 and Wordpress 3.2.1 ... checked and all my plugins are updated. Theme is BuddyPress Fun 1.3.9

Akismet version 2.5.3
Buddypress Group Calendar 1.2.8
bbPress Version 2.0
BuddyBar Widget Version 0.15
BuddyPress v. 1.5.1
BuddyPress Activity Comment Notifier Version 1.0.3
BuddyPress Activity Plus Version 1.2.1
BuddyPress Album Version 0.1.8.11
BuddyPress Docs Version 1.1.15
BuddyPress Like Version 0.0.8
BuddyPress Mobile Version 1.5.2.3
BuddyPress Private Messages for Friends Only Version 1.1
BuddyPress Usernames Only Version 0.58
Custom Login Version 0.9.4
Flash Video Player with HTML5 Version 1.2
MediaElement.js - HTML5 Audio and Video Version 2.2.5
oEmbed for BuddyPress Version 0.6-beta
oEmbed for Comments Version 0.6
podPress Version 8.8.10.12
Private BuddyPress Version 1.0.4
W3 Total Cache Version 0.9.2.4
WordPress Hashcash Version 4.6
WP-Polls Version 2.62
WP Best Practices Version 1.2
WP Widget Cache Version 0.25.4