What does this error message mean?

[Rakib]

I have opened some old modules of mine, with vst's made with older versions of OpenMPT. Im guessing some problems loading vst's. It would be better if the error messages could say which plugins faulted and maybe I could change them.

[Saga Musix]

Neither of those messages is by OpenMPT, so it also cannot show you the offending plugin. But you can already see which plugin of a module is currently being loaded if you have a closer look at the status bar.
I think I have seen the latter message before, IIRC it might happen if a SynthEdit plugin does not match the version the tune was made with.
The former message is probably also from a SynthEdit plugin (maybe even the same), in which case I would simply guess that it cannot load one of its SynthEdit modules.