Symptoms

K2SF Runtime Controls Attachment Control - intermittently get the following error: the file could not be uploaded. The network might be down or the file size is larger than the maximum size allowed
 

Diagnoses

If your Runtime and Designer use different Appool Accounts , the FileStore gives the above error because the FileStore can only be associated to a single AD Account per Server Session .
 

Resolution

Logged as a bug . Fix is being requested . To work around this you will have to set your Designer and Runtime to use the same Appool .