Definitely a vet visit.
Also, how old is your dog? If he's older (large and giant breeds age faster than smaller breeds) he could be suffering from arthritis, which could cause him to have issues on slick surfaces and/or with being jostled by another dog. Also, an injury could cause the same reactions.
If possible, laying down some non-skid rugs in the areas he's having trouble with would be helpful to keep him from panicking over his footing.
Also, how old is your dog? If he's older (large and giant breeds age faster than smaller breeds) he could be suffering from arthritis, which could cause him to have issues on slick surfaces and/or with being jostled by another dog. Also, an injury could cause the same reactions.
If possible, laying down some non-skid rugs in the areas he's having trouble with would be helpful to keep him from panicking over his footing.
