Massive Attack were due to play at Mad Cool Festival in Madrid in the early hours of Saturday (July 14) morning, but pulled out due to sound issues.
Mad Cool issued a statement saying the Bristol band cancelled "due to the sound interference of nearby scenarios", leaving many suggesting it was a clash with Franz Ferdinand, who have recently been remixed by Nina Kraviz, that led to the decision.
The festival added that the band tried to work something out but it was "impossible" to resolve.
Mad Cool apologised on behalf of both parties, but Massive Attack are yet to issue a statement.
Daniel Avery, Maya Jane Coles, Richie Hawtin, Sampha and Underworld were among the line-up for Mad Cool.
See The Evolution of Massive Attack below.
Dave Turner is Mixmag's Digital News Editor, follow him on Twitter