problems with libraries cause compilation errors?

Hello everyone,

I have this problem:

In file included from BlinkM.cpp:5:
/Marlin.h:50:21: error: WString.h: No such file or directory
In file included from /Marlin.h:41,
                 from BlinkM.cpp:5:
MarlinSerial.h:149: error: expected ',' or '...' before '&' token
MarlinSerial.h:149: error: ISO C++ forbids declaration of 'String' with no type
MarlinSerial.h:168: error: expected ',' or '...' before '&' token
MarlinSerial.h:168: error: ISO C++ forbids declaration of 'String' with no type
/MarlinSerial.h: In member function 'void MarlinSerial::print(int)':
MarlinSerial.h:151: error: 's' was not declared in this scope

I installed Arduino 0023 and put Sanguino-0018r2_1_4 in the right folder (arduino-0023\hardware). The old versions are necessary evil, I'm running an old 3dprinter needing an old Marlin firmware and it doesn't seem to work for newer Arduino versions.

But now I get these errors so I'm guessing I'm doing something wrong? The Wstring.h is part of the Arduino 0023 core...so I don't get this.

Hopefully someone here is more insightful than me and knows where to look to solve these errors? :) thanks!

Hopefully someone here is more insightful than me

No doubt. 8)

and knows where to look to solve these errors?

We'd need to see the code you can see - ALL of it.