(ShareCast News) - Iconic model railway, plane and toy car maker Hornby saw its shares fall 4% after signalling that revenues in the first half would be lower after problems with a new computer system and supplying model railways to Europe.In an update, Hornby said as the new computer system was introduced, trading was impacted throughout July and August, against a backdrop of a weaker general retail environment."This was in line with our expectations, but we are pleased with how the system has bedded down and encouragingly run rate volumes have since improved," said chief executive Richard Ames."They are now back to levels which are higher than last year. UK trading is now also benefiting from manufacturing production being ahead of plan in trains and Scalextric. Key new products for the Christmas trading season include the Hornby Silver Jubilee Collection Limited Edition Set and the Scalextric James Bond 'Spectre' Set."However, Ames said European sales are currently being impacted by ongoing problems with supply of international model rail sets."We are working hard to overcome these issues and we are confident that supplies of these products will improve in time," Ames said.He added the company expected further disruption as the computer system was rolled out across Hornby's European business in the second half of the year, but could not predict the impact on trading.Despite that, Ames said he was confident full year results "will show progress on last year"."The group is now looking ahead to the important Christmas trading period. Early indications from our customers are positive and we have an exciting pipeline of new products that are being well received," he said.Hornby shares were down 4% to 101.26p at 1233 BST.