I have a solution (which has about 60 different databases link together) that was created with filemaker 6.0 and worked well, however when I moved it to fm7 and try to open one of the main databases I keep getting the following message: "This record can not be modified in this window because it is already being modified in a different window"... Anyone knows what this mean or why it is doing this? any help would be appreciated

It means another window (or file) has the record in an uncommitted state.

With FM7/8, it is necessary to explicitly commit changes to records. This is easily done by adding Commit Records[] steps to navigation and process scripts.