Usually this occurs because the previous AntiVirus product didin't uninstall properly or was left on the PC, Which causes a conflict and the delays you are experiencing. Most major AntiVirus products now have special uninstaller 'clean-up' programs available to resolve this problem, including OneCare itself.
The other possiblity is that somethin simply went awry with the OneCare installation, which can usually be repaired by performing an uninstall and then re-installing OneCare. The quickest way to be sure you've covered most possible reasons for the issue is to uninstall OneCare, run the clean-up tools for both OneCare and the other old AntiVirus product, and then re-install OneCare.
A quick clue to whether the old AV is the culprit can sometimes be found by looking in the Windows Security Center. If the old product is still displayed there it's almost assuredly part of the problem, though it might still be even if it isn't.
OneCareBear