PP acts strange- cant link clips and so on

I recently (in late february) opened a project that I finished in november to correct some issues. But there was a lot of strange things that ha happened since last time....

-  a lot, ok maybe 7-8, videoclips that never had been editied in to the project suddenly had replaced some clips...

- and this strange phenomena occur in all saved older versions of the project (it´s like I´ve saved this wrong clip a long time ago, but I havn´t done that...)

Ok. I replaced them with the correct clips but then the next strange thing occured:

- some clips is completely black. I can ses the edited clip with the correct "name" in the timeline and tries to replace them, but the "link media" wont work. I can find the clip in the "project frame/list". How do I do to connect the clip again?

Thaks in advance