I do at least one PT a week and use lots of protein in my products. The only time I remember having an issue was when I used gel with protein (Giovanni LA Naturals comes to mind.)

As pedaheh said, it could be the particular protein. Why don't you try the protein in the other products--but not the protein gel?? and then do the opposite and see if you can narrow down the problem. The other thing to try is one product with protein and the rest with none and see if you can identify the particular protein.
3a (Corkicelli), highlighted, fine, low porosity
modified CG, since April '07
CG since 3/11/08

SE PA

HGs: Anything Sevi; Curly Kinks Satin Roots, Curlycue ReNew and Coil Jam; homemade FSG and okra gel; soap bars; UFD Curly Magic; Botanical Spirits Jellies, CJ Repair Me, Marie Dean Leave Ins and Curl Creams