"One or more field types are not installed properly. Go to the list settings page to delete these fields."

I received this error while using an SPQuery CAML query string. the problem was that I had renamed my Title column in the list to “Document Library Name” and in the SPQuery i was using

query.Query = "<Where><Eq><FieldRef Name='Document Library Name'/><Value Type='Text'>" + this.workflowProperties.List.Title  + "</Value></Eq></Where>";

after some research I found out that the internal name of the column was still ‘Title’ so i used

query.Query = "<Where><Eq><FieldRef Name='Title'/><Value Type='Text'>" + this.workflowProperties.List.Title  + "</Value></Eq></Where>";

and the error was gone :D