4.1.7 Slow To Respond To SMB Network Discovery...

mdgm wrote:
The NoSMBDisconnect add-on makes a reversible configuration change. It's not risky to run and many users have found it to be helpful on several versions of RAIDiator. Unless you have a huge number of users you probably won't have any issues using this add-on.

This will not resolve the problem: the first SMB access of every PC will still be slow. Only subsequent requests will be faster. And I do not know about negative impacts caused by not releasing unused resources on the NAS; that sounds like a resource leak situation which can only be resolved by rebooting the NAS. That's then worse than the current situation: all I need to do now is to toggle the CIFS service once after I've restarted the NAS; then all(!) PCs will be able to access all shares w/o any delay from the very first time.

I suspect that there's an issue with the boot sequence. Maybe samba is started too early. If it is started last, no problems occur.
Actually, Sean has mentioned this suspect already in December 2010:

Jedi Knight, This behavior suggests that a change in the way the new firmware boots the device has a damaging effect on the CIFS/SMB discovery mechanism. Please forward this issue to the appropriate team such that we can all enjoy a fix as soon as possible. Thanks, Sean