Many business users Thursday experienced serious problems with the Admin Console in Google Apps for Business.

A Google Apps status email said that some users reported that the Admin Console was totally unusable because it continued to refresh endlessly, and never fully loaded. VentureBeat found this to be the case as well.

Google posted this message at 4:11PM Thursday at its Apps Status site: “We’re investigating reports of an issue with Admin console. We will provide more information shortly. Users are seeing the Admin console refresh continuously on loading.”

Almost two hours later, at 6:05PM, Google posted that it had fixed the problem. The company never made clear how many Admin Console users had been affected.

Google has been pushing hard to unseat Microsoft productivity and communications services in medium and large enterprises in the U.S., and has been enjoying a good deal of success. Google says that more than 5 million U.S. businesses have now switched to Google Apps. That’s why reliability problems like the one today are troubling.

And the problems weren’t confined to the one with the Admin Console Thursday. On Wednesday, several key Google services experienced problems between 3PM and 5PM Pacific time.

Google acknowledged problems with Gmail at 3:38PM, then posted another update at 4:19PM saying that the problem had been fixed. The latter post contained this message: “Delayed messages will continue to be delivered, and we expect all messages to be delivered within the next hour.” Again, it’s unclear how many business accounts were affected.

Problems with the Postini email security app were reported at 3:38PM Wednesday and were not resolved until 4:38PM. Google gave no further details about the problem.

Google Analytics also had problems Wednesday. This update was posted at 3PM Pacific time: “We’re experiencing an issue affecting less than an estimated 5 percent of the Google Analytics user base. The affected users are unable to access Google Analytics.”

That problem, however, was resolved just 21 minutes later.