From Bankrate.com (and Boston.com): http://www.bankrate.com/finance/c...ined-1.asp
1. Credit card company does not like your charging patterns (say buying "cash-equivalent" items regularly).
2. Credit card company does a hard closure on your account.
What to do:
1. Let the credit card know in advance of a large purchase.
2. Go online frequently to double check the health status and credit line for the card you are going to use.
3. If declined, call on the spot to resolve any issues.