Conspiracy theories abound but Microsoft is swearing blind that the block on Instant Messenger users being able to share YouTube links at the weekend was just a glitch.

IM users were faced with the block on Friday evening and Saturday morning, which led to blogs aplenty that the computing giant was blocking the Google-owned site on purpose.

However, Microsoft has been quick to say that the problem was caused by the third party that handles blocking of potentially unsafe content for MSN Messenger and Windows Live Messenger.

"As some of you noticed, we had a problem from Friday night to Saturday morning where our Messenger service was incorrectly blocking some legitimate IP addresses", a Microsoft employee said on the company's Messenger blog. "We sincerely apologize for any difficulties this caused our users."

Microsoft went as far as to throw out some of the speculation of the "real" cause of the problems.

"Microsoft did not request to block any of the URLs that were accidentally blocked", it said in the blog.

"The blocks were made by our partner as a result of their process to block harmful URLs. We are still investigating the specific reason our partner made these incorrect blocks and we will work with them to improve their process for detecting harmful URLs while not blocking safe ones."