Both clubs had the paperwork in place before the cutoff point, but the Sunderland manager revealed, after watching his team limp to a goalless draw with Stoke City, that network problems caused the delay.
Bruce, whose only other business yesterday was to land Tottenham defender Alan Hutton on loan for the rest of the season, was desperate to add Benjani to his ranks after allowing Daryl Murphy and David Healy to join Roy Keane at Ipswich.
We have done everything we possibly could, said Bruce. We did inform the Premier League and the FA and we were there at the training ground and it was done before the deadline.
We have had huge difficulties with faxes, email and I hope common sense prevails.
I hope we are told it has been completed in the morning.
Talks with Benjani, a Zimbabwean international, were revived after a deal initially broke down over the weekend because of wages. Bruce, however, had to have a rethink after learning there were few available alternatives.
Bruce was relieved to see one of the two new full-backs he craved arrive, with Hutton joining until June moments after long-serving Nyron Nosworthy was allowed to move to Sheffield United for the remainder of the campaign.
The Glasgow-born 25-yearold, priced out of a permanent switch to the North-East earlier in the month because of a reputed £8m valuation, had spent the best part of two days at the club before the move was confirmed.
Hutton will be available to face Wigan on Saturday.
The Sunderland boss knows something is required to lift morale, after failing to record a win with the exception of an FA Cup success over nonleague Barrow in 12 matches.
Referee Howard Webb hardly helped, by failing to award a penalty for a clear handball from Robert Huth and refusing to send off Dean Whitehead when he kicked out at Lee Cattermole just before half-time.
It was a blatant penalty, a blatant sending off and they could be defining moments,
said Bruce. The penalty I have just seen and the linesman was ten yards away looking straight at him.
You can see we were a bit nervous, edgy, the effort and endeavour was there.
We gave the ball away too often. There were little signs and now we hope to turn it around on Saturday against Wigan.''