[bartekdvd]

The input line is too long. PAWN compiler does not support such long lines - the number of characters in one line is limited. Try this compiler: https://sampforum.blast.hk/showthread.php?pid=2768123#pid2768123 it fixes this problem (actually it just increases the limit). Direct download: http://www.mediafire.com/?jqz4785ym821g5x just replace pawnc.dll and pawncc.exe in pawno folder. ZCMD uses #define directive for command definitions and preprocessor treates everything after #define as a single line.

OR

You can define your string before:
new long_string[] = "bla bla bla...";
...
CMD:command(playerid,params[])
{
ShowPlayerDialog(playerid,DIALOG_HELP,DIALOG_STYLE _MSGBOX,"Help:",long_string,"OK","");
return 1;
}