I would try out "nucleofection" for your primary B cells. Whereas commonly used transfection protocols (e.g. lipofection with FuGene, Lipofectamine, Effectene etc) work very efficiently in cultured cell lines, they are very inefficient for primary cells so it is not surprising your colleague is having difficulties with primary B cells. The "Nucleofector technology" is a non-viral method that was developed initially from Amaxa (recently acquired by Lonza) (http://www.amaxa.com/). It is based on electroporation that uses different combinations of electrical parameters (electrical pulse intensity and length) as well as specialized solutions for different primary cell types, which facilitate the transfer of DNA/RNA into the nucleus. Although the exact mechanism of the transfer is not known, many studies have used nucleofection for transfecting primary cells including B cells, and compared transfection efficiencies and viabilities with other methods, and it is well reported that nucleofection indeed works very well (much higher transfection efficiencies with good cell viability without the need of too many cells to start with). It works for stimulated B cells and transfection efficiency is reported at >40% from published studies.
Have a look at Hamm et al (Tissue Eng., 2002) (compares nucleofection with other methods for different primary cell types), Gresch et al (Methods, 2004) (also a detailed comparison between nucleofection and other methods using B cells as well) and Seiffert et al (Leukemia, 2007) (a study on how nucleofection of B cells with circular DNA was found to differ from nucleofection with linearized DNA or RNA, you might want to consider this study). Lonza provides specific kits for nucleofection of primary B cells so I suggest you get a hold of these special solutions and electroporation devices they provide together with different electroporation programs for B cells, you should definitely find conditions that should work out for you. Hope this helps!