Viewers reported the channel cutting out during the Scottish news programme at around 6.30pm on some networks including Sky and FreeSat.
However, the broadcaster's programmes stayed on screen for viewers watching via the Freeview service.
An STV spokesman said the glitch was linked to a network transmission issue on some platforms.
It affected the start of the eagerly-anticipated documentary about Scotland's constitution, Road to Referendum, presented by Herald columnist Iain Macwhirter, which aired at 8pm.
STV said the programme will be available on STV Player and is repeated this week. A spokeswoman for STV said: "We apologise for lack of service due to a network transmission issue on some platforms."
Lorna Robertson, 67, from Aberdeen, was watching the Scottish news on STV when the channel went blank at around 6.30pm.
She has two televisions in her house, one receiving through Sky and the other through FreeSat, but both displayed the same message: "The channels is scrambled or currently not available."
"We were particularly wanting to watch Road to Referendum," she said. "We were watching the Scottish news on STV, so I think that was interrupted at about 6.30pm."
Mrs Robertson said she had been unable to record the progamme either.
Another viewer tweeted: "ITV London is working still, but everything else just vanished. I did ask them but nobody answering me."
Mr Macwhirter tweeted later: "For those who missed #roadtoreferendum due to technical problems at STV it'll be on STV player tonight and repeated later this week. I hope."