From what I understand, you see cyclin B1 non-specifically in your control (mIgG) IP which means that either the antibody or the Anti-IgG on the beads are pulling cyclin B1 down. What you can do to clean up the control lane is increase the number of washes (volume & duration--I get good results with 4x10 min on a mixer with 1mL wash buffer for 50ul of bead slurry) or increase the stringency of the washing solution or both until the control lane clears up. Initially, I usually run 4 IPs in parallel with increasing wash buffer [NaCl] from 150mM to 1000mM and then you can see which [NaCl] gives the most specific result for your future replicates.

Alternatively, you can increase the stringency of your wash buffer by adding anionic detergents like SDS and/or DOC. You need to play with the concentrations so that on the one hand you get a clean blot, but on the other hand do not lose too much of the specifically bound protein.

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