Are you using a UV/VIS spectrometer or spectrophotometer? There is a big difference in the instrument setup and parameters. The spectrophotometer uses a monochromator to separate the individual wavelengths of light. With a spectrometer, an interferogram is collected and transformed to a spectrum by means of a fourier transform. There are also diode array instruments that collect the entire spectrum at one shot by exposing it to an array of diodes, each representing a different wavelength of light.
If this doesn't ring a bell, can you list some of the parameters that are available to modify?