Old text-message tweets being reposted as new ones

Tweets I sent from my phone via SMS over a week ago are reappearing as entirely new tweets. As far as I can tell the original txt tweets don't go anywhere, the content is just reposted entirely. (For example: http://twitter.com/coldacid/statuses/... is the original tweet, which Twitter reposted three days later at: http://twitter.com/coldacid/statuses/... )

I had originally considered this to be an issue with my mobile service provider sending them multiple times, but I found out that some users with another service provider have the same problem. My provider is Telus; the other one with the same problem is Rogers. Seems that Bell Canada is not affected.