Basler Camera Problems
I would recommend contacting Basler. As a scientific camera company they are used to answering user type quesions and they should have application engineers to point you in the right direction including picking lenses. As far as picking a lens, can you say a little more about what you are taking pictures of? I have a couple of general purpose C-mount lenses in mind that I use for most industrial applications that are available from the Edmund Scientific catalog, but it really depends on what you are photographing if they are suitable.
I have not used Basler cameras myself although I know they are one of the better scientific camera makers. (I use other similar brands.) But also check out if they have a users forum on their website. I do not know if they do or not, but if they do that would be a good resource. And of course, read thoroughly any manuals they provide (usually done only in a throes of absolute desperation I know, but worth a try, especially before contacting Basler as any support person will appreciate it if you took that first step. Also it will speed up them being able provide constructive comments if you are familar with what documentation is available.)