TOPIC:

it's in fact weird

I tested our clients on W10 (64), XP (32) and Linux Mint (64) - all run without issues. Haven't heard of similar issues among the people that use our clients. Maybe your attempts to change "innerhighlight.grf" are the cause of it, but not sure. I suggest the follow steps:
- Download the zip archive here , extract and replace all files in the Game folder;
- Extract files of BTPro client to the same folder, replacing when asked;
- Set properties of openttd.exe to "Run as Administrator";
- Optional: put the openttd.cfg (or create an empty openttd.cfg) in the same folder as the executable, instead of User Documents folder;

I think it's all ^^

Note: Current clients have problems when using trams - Solution will be released as soon as we found it ^^

When I do all steps you write, then it works.

If I only extract BTPro client and start the .exe, it didnt work.

SkyBrutus wrote: When I do all steps you write, then it works.

If I only extract BTPro client and start the .exe, it didnt work.

I guess it's because the steps I mentioned are the correct ones ^^
And are very important when a new OpenTTD version is released, specially the major ones (yearly and usually on April 1st).

Anyway, I think all works good now for you