No log file in C::B's directory?
Maybe you can have some clues if you run C::B's from console, too.
It seem your problem started with re installation of mingw, are paths in C::B correct?
Log file: no, I do not see any log file in directory of CB.
Console: thanks for idea, I'll try it next time. When I work on GNU/Linux, I do it as one of the first attempts to solve the problem but on Windows I often forget, because almost all programs I had problem with didn't print anything when I tried...
Paths: I'm totally sure this wasn't the problem. Because as one of first steps of solving this, I deleted all obj files and also the executable one to be sure they're compiled, not reused. And executable WAS created; I run it manually and debugger was able to run it, too. Only button (and key shortcut) ignored it with no message.
Anyway, it happened again, but this time with other compiler (before, it was MinGW, this time it's MS VS 2008) but in this case I also know what problem was - I turned on opinion "treat warnings as errors", then unused function parameter generated warning which was converted to error which caused that linker failed - but C::B didn't notice that and after finishing closed log tab. But unlike previous case, this time these errors were still logged in log tab. But I thought I should write this here for others to help - in this case, problem was that "there was a problem not highlighted by CB which caused creating executable to fail".