I've suffered from this problem for the past year or so. There are some others who have brought up the problem in the past, but as it is a Sharepoint / System issue it was not resolved.
I have finally found the source of the problem and found several solutions, so I'm sharing it here.
My computer is Win7 and I'm using Toad for DB2 Expert Edition. I use automation for several tasks. One of them is to save some Excels for the users to check the Organization Users security settings. These change according to the Roles assinged to them in SAP. I save these files to Sharepoint.
The work-around that I discovered was to keep any file on the Sharepoint server open for writing. I had to remember to open this file before I left the office.
The cause of the problem ( as I understand it) is that the Windows service that looks up server names, times out after about 8 seconds, and if you are not connected currently to the Sharepoint server, Windows may time out.
The simplest solution that I currently use is to map a Drive to the Sharepoint path. It is interesting that Toad would not allow me to enter the mapped file name, but still it solved the problem.
Another possible solution is to change some of the parameters in the Registry under HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\NetBT\Parameters
One of setting you can change is the amount of time that Windows times-out, but that will effect you every time you enter a wrong UNC path.
Another setting you can change is the amount of time a Session remains in memory. This will not help if you restart the Computer.
Another possible solution is to to map the Server in the hosts file. I did not test this solution, but I assume that it should do the job.