I don't have SIW so I don't know if it's one of the Applications CCleaner cleans. In Ccleaner, click the Applications tab, near top left next to Windows. Scroll down to see if SIW is among the listed Applications. If so, uncheck any/all the boxes you don't want cleaned by CCleaner in the SIW listing.

If SIW isn't listed, it may be something else cleaning out your password list - such as WiseCare Pro, for example.

Do you routinely save your Registry cleanup items in CCleaner? If so, Right-click on the saved .REG file/s that was/were most recently created and select "Merge. Maybe the SIW passwords were stored in the Registry and are recoverable - if you're very lucky.

Good luck.

Jim.