Symantec has cut its sales forecast for the full year, prompting a 9% fall in its share price.
Earlier this week, Dell cut its sales and profit forecast for the third quarter, precipitating a 5% share price fall. Hitachi also posted a half-year loss this week.
The results reflect a tight IT market with most firms struggling to increase margins.
Symantec posted a second-quarter net loss for the period to 30 September of $251m (£148m), compared with a $135m net profit for the same quarter last year.
The quarter's net loss included $284m in costs related to Symantec’s multibillion-dollar acquisition of data storage company Veritas.
Symantec's sales for the quarter increased to $1.19bn (£700m) from $1.10bn. But for the full year the company forecast revenue of $5bn, which was below both Wall Street estimates and previous company forecasts.