Unexpected Error 41

Something strange happened today. I wanted to update the FW of my PL3 from 5.05a to 5.05f in order to try resolving various problems with the today received Eheim controller...
I always update by using the special serial RS232-cable and worked fine till 5.05a. But now, when I want to establish a connection, PLC (5.0.53) replies with 'communications error 41!". A reboot of the PL3 also didn't help.

Does someone have any idea what the problem is / error 41 means?

Btw, a downloadable errorlist of all possible errors would be nice.

Disable the Eheim-Controller in ProfiLux menu Extras->Eheim first.

Thanks Frank. That solved it! FW is now upgraded to version 5.05f. Unfortunately, I still have the same problem(s). I shall start a new thread for this.