Problems with tikzDevice when using certain Latex commands

[Martin Schmelzer]

Hello everyone,

I have a long presentation (10000+ lines of code) including several code chunks and plenty plots. The last couple of weeks I had no problems compiling the presentation. But today I started having problems. Somehow not a single plot was produced anymore. Investigating the log files I encountered the following error which can be found amongst other related topics on the www: 

TeX was unable to calculate metrics for the following string
or character:

    m




In addition I can observe that the *-tikzDictionary file stays empty during the compiling process.

I am still not 100% sure why I have problems now. But right at this moment it seems like commenting out the following lines does seem to solve the problem: 

\setlength{\OuterFrameSep}{-1pt}
\makeatletter
\preto{\@verbatim}{\topsep=-10pt \partopsep=-10pt }
\makeatother

I added them to change the spacing of code chunks and their output in the resulting pdf document.

Any thoughts on what exactly happens here?