These kinds of issues pop up when there is a conflict between IDM and other applications. To rectify it, you can try either of these steps:
- Uninstall your security system or antivirus software as some programs do not allow accessing their files if you have an actively running antivirus software
- Go to Options of IDM, open Connection IDM and set the number of parameters to 1
- Move the temporary folder and the destination folder into the same drive
- Try restarting your system and resume your download
