I've seen this problem before. Currently there's actually no way to delete Invitation requests. I do hope that this feature is implemented because that can heavily clutter a group but I also think the owner should be more consulting before who they invite people in. If the owner is inviting 77 people and they've either ignored the invitation or unwilling to join then this is basically invite spam.
But for the time being you should suggest this feature and hopefully when davjs get's around to it, it will be added because it would be useful. Hope this helps. :)
Post edited at 11:15 pm on July 5, 2009 by Charolastra
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y'all nukhuhs that be aight wit dat bullshiiit, just hit us up mang