Imagine owning a company moments away from closing an important deal, but when you go online to transfer the money from a business account, you can't get to it. You can't wire it either, because your bank is suffering a computer system “blackout.”

You lose out on the deal. What now? A lawsuit may not be the answer.

“You probably are not going to recover much, if anything,” said Richard Roth, founding partner of the Roth Law Firm in New York City. Proving the lost deal was the result of bank negligence would be very difficult, he explained.

Wells Fargo & Co. went through such a “blackout” starting last Thursday. It was partially restored on Friday. Late Monday Wells Fargo spokeswoman Hilary O'Byrne said, “Most systems and services have now been restored, though customers may still experience longer phone wait times than usual. Our branches are open.”

O'Byrne did not respond to a request for an interview and general counsel Allen Parker did not return a message requesting an interview Monday.

On Feb. 7 and 8 the bank issued online statements saying an automatic power shutdown at a main data-center facility caused the system issues. The automatic shutdown was triggered by a smoke condition created by routine maintenance activities in the building, it explained.

The bank said applications were “systemically re-routed to backup data centers” during the shutdown. But ATMs, mobile and online banking systems were temporarily knocked out as well as branch bank systems.

“We apologize for the inconvenience caused by these system issues, and we want our customers to know that any Wells Fargo fees incurred as a result of these issues will be reversed,” CEO Tim Sloan said in the statement.

“Our recovery from these issues was not as rapid as we or our customers would have expected,” Sloan continued. “We will review the system issues in detail, and do all we can to ensure that this type of disruption doesn't happen again.”

Roth offered several scenarios involving different types of clients—a charity, for example, and an individual—and concluded any case would still be difficult to prove and to recover damages.

Besides, he said, most banks have customers sign use agreements that eliminate the possibility of a class action lawsuit and impose mandatory arbitration for any dispute. He said they also usually limit the amount of damages due to things such as computer outages.

“I lost the internet [for] two weeks once and it drove me crazy,” Roth added. The good news is that in the last five years these systems have improved greatly, he added.

“Everyone has outages,” Roth said, “but generally it's pretty damn good.”