This message is generated if the iterative singular value decomposition algorithm for inexact numbers does not converge. This algorithm is used by NullSpace, PseudoInverse, and SingularValues.
If you see this message, and there is no obvious reason for lack of convergence, please send your example to Technical Support so that it can be investigated.
Off[message] switches off the message; On[message] switches it on. For example: Off[General::cfail].