There are troubleshooting guides for HPLC, a related chromatographic technique. In many instances the troubleshooting is similar. The HPLC troubleshooter (http://www.dq.fct.unl.pt/QOF/hplcts.html) online interactive guide can be useful for IC as well.
There are several common issues that show up in IC, see if you can think about these chromatograms and what might cause the problem.
Sample Chromatogram 1
If you look at the first big peak, the shape is quite a bit different than the other peaks. It is very broad and has fronting to the peak. This is due to overloading the column, thus there is not a great separation sodium peak, and it dwarfs any other peak that would have a shorter elution time. This sample was from a tidal river, thus the high sodium concentration.
Several other common issues that show up in IC are if the suppressor column starts to fail, the eluent solution changes either in pH or ion concentration, or the analytical column gets contaminated. These tend to cause baseline drifts or very poor peaks.