Why a dialup connection dialog during boot?

My Win98 system has suddenly started to present a DialUp connection dialog box during the boot process. Task scheduler is disabled; there is no entry in the Win.ini e.g. load= or run=, or in System.ini, Startup folder checks OK. Have tried initiating the dialup to see where it leads to but it merely makes a connection and no webpage is opened. There must a number of entries somewhere 'cos I have to hit the cancel button a number of times before the final (10th?) dialog cancels and Windows continues to load...
Any ideas please?