Does your saw have a kickback chain brake (usualy activated by the front hand guard). This may have been 'tripped' when the new chain was fitted.
The 'professional' who fitted the chain really should have checked operation of machine after fitting a new chain. It would probably be as well to pop saw back to whoever fitted chain for them check what has happened. In the 13 years I spent sharpening or fitting new chains it was always considered good practice to check operation of the saw before its return to the customer.
Robin S
August 2008