The path of the item 'http://localhost/Reports/Pages/Folder.aspx?ItemPath=/Parent Reports/Child Reports' is not valid. The full path must be less than 260 characters long; other restrictions apply. If the report server is in native mode, the path must start with slash.

Hi folks,
I got the above error after immediately fixing the dataset has to be deployed error while trying to deploy the ssrs report.
The reason for this was I had my report name as Report Check $2,000. All I did was remove the $ sign and the , sign and bingo I was able to deploy the report.

So my suggestion to resolve this error is that you should try not to add any special characters in the name of your reports.