Not much to my surprise (this is not the first time my employer has done a provider change in the 25 years I've worked for them), as the changes propagated through their system and into Quicken, a huge phantom value turned up on my account that isn't really in the 401(k) plan. It seems to be an artifact of how Quicken interprets the transaction feed they get from the provider, and it injects a large (roughly 5% of the total value of the account) "cash balance" into the file. That money isn't really there compared to what the real balance is when I look it up online. Again, based on past experience, I need to give it about a week or so to see if the transactions ever catch up, and if they don't, I need to go in and manually adjust the cash balance in the account to the real balance, which is generally $0 as the 401(k) plan does not hold cash on hand from my paychecks, but just allocates it amount my investments.
I'd be more worried about this if it hadn't happened before. I hope that the downloads from the the new servicing company work better than those from the existing one, though.