Hi AnnaPoj
It is known that any anti virus/protection software must be set to exclude MYOB from its scanning, otherwise it will definitely slow it down. First scan MYOB manually, then when happy it is safe, set your protection software to exclude MYOB from future scans.
Having said that, it will slow down all of MYOB not just In Tray - so there might be another issue with In Tray that MYOB is not aware of.
While you have not changed your settings, a new version of MYOB have been installed and in a different location to the last. Nortons may have been see to exclude the previous version - by you or someone else. It is important when setting an exclusion, you select the entire MYOB folder (and all subfolders), rather than a specific file.
I suggest you check and update the Nortons settings - ensure it is set to exclude all files in the AccountRight folder at this location:
C:\Users\<your windows user name>\AppData\Local\Programs\MYOB\AccountRight
This is the default location. Setting it here will prevent the need to update this setting each time MYOB updates.
If unsure how to set/check exclusions in Nortons, check your Nortons documentation.
Regards
Gavin