There can be one of the following two reasons why "bundle" won't open:
Reason 1: When a workspace contains projects that are outside of the workspace folder, the "bundle" option of the archiver creates workspaces that cannot be opened.
Solution: If the main design is inside the workspace, exclude the offending projects (right click project in workspace explorer and select "Exclude") but make sure that they are included as dependencies. The software will include them in the bundle correctly. When opening the bundled project they can be manually restored if desired.
Reason 2: When bundling a workspace (.cywrk file) that is in the same folder as one of its project files (.cyprj file) the resulting bundle cannot be opened by creator.
Solution : The resulting bundle will have a top level folder similar to XXX.Bundle01 which contains a file similar to XXX.cyprj. Rename the top level folder XXX.cydsn if XXX is a design project, or XXX.cylib if XXX is a library project.
These issues will be fixed permanently in PSoC Creator 2.1 which is expected to be released by end of June 2012.