Error: Some text layers contain fonts that are missing. These layers will need to have the missing fonts replaced before they can be used for vector based output.
You shouldn’t worry much about this message. It is just Photoshop letting you know that your version of the font file and the one the designer has are not the same. So if you allow PS to update the layers, no harm will be done. What is more important is a “Missing Font” error, which means that you don’t have the font that was used. Having a designer rasterize or convert all layers to shape (outline) all of the font layers before they send them to you would take care of this issue. Given that you do not intend to edit the text, there will be no difference if you have it as an actual text, or a mere shape.
Error: Some groups were found corrupted and repaired.
Technically, everything you need to know can be retrieved from the text of the error. It has a mere informational character. The problem has already been fixed by Photoshop.
Error: This document contains unknown data which will be discarded to keep layers editable. To preserve the original appearance instead, choose Flatten to load composite data as a flattened image.
This error lets you know that the version of Photoshop the designer has is more advanced than yours (Photoshop Extended and/or a more recent version). For this matter, some features included in the designer’s version are not recognized by yours. This can be exemplified by 3D layers or Smart Filters. This can be solved in no time if you contact your designer and discuss this error. Alternately, updating to CS5.1 or CS5.1 Extended will also ensure this error won’t show up anymore.