"The given key was not present in the dictionary"

Error message when activating a feature with field definition included. Could not display any site columns via the site either. Fired up SPM and browsing the Fields collection and got an error message about a field type not correctly installed.

It turned out I had misspelled "Number" to lowercase "number" in my field definition file. Amend the line and upgraded the solution and the problem was resolved

WSPBuilder: Unicode characters

Got this error message from WSPBuilder when building a new WSP file:
"The filename of the CAB file must not contain Unicode characters!"

I had some some swedish characters in my projectfolder name. I removed it and updated the SLN file with the new path. Problem solved.

// Henrik