“Martin” star Tisha Campbell and her husband Duane Martin have been sued by City National Bank for more than $430, after allegedly defaulting on a 2008 loan for their  Lake Arrowhead, California home.

According to legal docs obtained by TMZ … Tisha and Duane (an actor who starred in the ill-fated “Paul Reiser Show”) took out a $625k home equity loan on a slick waterfront property in Lake Arrowhead, CA .

At the time of the loan the couple still owed more than $730,000 on their mortgage to ANOTHER financial institution — Aurora Bank.

Long story short — Tisha and Duane allegedly defaulted on BOTH loans. Earlier this year, Aurora foreclosed on the home … and according to the docs, the bank sold it at auction for $925k.

Aurora got paid first … and sent the remaining $192k to CNS to partially satisfy the home equity loan, which had already ballooned to $633,119.52.

City National is now going after Tisha and Duane for the balance.

The rep points out that CNS received a $400 million government subsidy in 2009 to help people like the Tisha and Duane through the mortgage crisis … and says, “In this case City National refused to share the significant benefit that they received with the Martins.”

The Martins are now threatening legal action against the bank — claiming the bank discriminated against them.