What type of "Flickering" is being experienced?
- Is it a "Pulsating" type of flickering, with "Brown Corkscrews" flowing inside the Lamp?
- Is it a random, non consistent flicker, with possible audible sizzling sounds at the fixture - or "Noise" in the form of spuratic lines seen on Television, in the lower VHF channels (2 through 6)?
- Is it repeated flicker across one Lamp?
- Is it transient, short term flicker on all lamps of a given fixture?
- Do any other fixtures act funny - if yes, what is observed?
- Are Incandescent Lamps dimming and flickering while the Fluorescents are?
If #1 is observed, this may be associated with new Lamps' "Burn-In" time, and should cease after a few days.
Another reason may be very cold conditions, and moisture ("corkscrewing" is normally related to dampness and cold)
#2 scenario is when the pins of a Lamp are not seating properly in the Lampholder.
Spin the Lamps around to verify proper seating.
If the Ballast is an Electronic Instant Start type, verify that you have connected both wires at the Lampholder to the Ballast lead wire.
Electronic Instant Start Ballasts typically only have one lead wire to each Lamp at one end, and the opposite ends connect to a single red lead from the Ballast.
Scenario #3 indicates a poor connection on a Lampholder, or a Lamp which is failing prematurely.
This may also indicate a Ground Fault issue from a Lamp lead, or a bad circuit in the Ballast.
Scenario #4 would indicate a drammatic voltage drop occuring very rapidly, which may be from any external loads on the same circuit as the lighting.
Check over this list, plus the one from Mark (E57) and let us know what's up.