... There is no lame.exe in the plugins-folder but should I try to replace the in_mp3.dll with the lame_enc.dll?
In_mp3.dll is the decoder plugin. It is an internal program component. Do not touch it.
Normally MC downloads the lame.exe and gogo.exe components when MP3 encoding is first accessed (it is enough to open the MP3 encoding options window). Perhaps your firewall is blocking the access.
However, since you already have the lame.exe binary you can simply copy it to the Plugins folder. In addition, the gogo.exe file must be present even when it is not used (the "faster MP3" option uses gogo.exe). You can download gogo.exe separately from
here (unzip and copy gogo.exe to the Plugins folder).
-V 0 --vbr-new
This is the same as the internal "VBR Extreme" setting so you don't need to specify a custom command line when you use the internal MP3 encoder.
Regarding the external encoder problem, I was able to reproduce the crash. I ripped a three track CD single using the internal MP3 encoder and the external encoder. MC used the same lame.exe file in both cases. "External" crashed after the first track. The log files are in the attached zip package.
I also noticed that the secure mode was unusually slow (about 1x) with any encoding setting, but I must further investigate the problem before reporting anything.