Are you getting a 'buffy coat' - a brown-grey mass of cells at the interface? Ensure that you are using hypaque 1077 or other Ficoll gradient at ~24dC, with very careful Ficoll underlay/medium overlay, and centrifugation at ~1350g for ~7 mins, no brakes. Following this round of centrifugation, get the interface layer which is enriched for PBMCs, and wash with 8-10x vol HBSS/culture medium (i.e. for 1.5 ml of interface removed, fill the 15 ml tube with HBSS) at 350g for 5 mins. When this cell pellet is resuspended, you'll end up with a nice single cell suspension.
As for the RBCs, thats probably a direct consequence of overloading the gradient. If you still see a very red pellet at the wash step above, just perform a Gey's or AmmCitrate lysis for RBCs.