Philips mp3 player sa6045
This player shows the "Do not disconnect" message when it is doing something critical such as transferring tracks or updating firmware, which could corrupt the player if disconnected part way through.
The player shows the "OK to disconnect" when it is idle. As the message says, it's ok to disconnect, as the player will not corrupt if disconnected when it is idle.
These messages mean that the player does not need the "Safe to remove" procedure.
It is ok to disconnect part way through charging. Also the player will condition the battery once it is fully charged, so it's ok to leave it charging.
Occassionally batteries can "memorise" when constantly disconnect and reconnected without fully charging and discharging. To help prevent this, fully discharge the player (leave on until dead) and fully charge and condition (leave charging for about 12 hours) every couple of weeks or so.