MTV was found to have exceeded the rules on 15 separate occasions across its portfolio of channels, which include MTV, MTV2, MTV Dance, MTV Base, MTV Hits, VH-1 and VH1-Classic.
On nine of these occasions, the excess was 15 seconds or less, but on another six occasions, MTV exceeded Ofcom's Rules on the Amount and Distribution of Advertising by more than four minutes.
MTV said the breaches were a combination of a new computerised advertising airtime booking system and programming either over or under running.
Despite assurances from MTV that it had tackled the problem, errors had continued to occur.
Ofcom said: "The licensees should note that if further breaches occur, Ofcom may need to consider further regulatory action."
Separately, Ofcom has upheld 78 complaints about violence in an episode of 'Eastenders'.
The regulator said the episode, which featured a gang attack in the 'Queen Vic' pub, exceeded viewers' expectations for a drama and was too violent for a pre-watershed drama when children may have been watching.
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