An investigation is under way in the University of Limerick into timetabling problems which caused severe disruption in the first week of term. Several groups of students lost their classes completely, according to the students' union, after a computer software failure resulted in errors in the master timetable for the first week of term.

So significant was the disruption that the new president of UL was moved to apologise for the problems in an email to staff. The union is now concerned that students will be "expected to cram 13 weeks of work into 11 full weeks of term". It wants longer hours for library and computer facilities and has asked that "no student be examined on a topic they haven't been lectured on". The union claims the problems were caused by inadequate resources given to an overworked student services department and what they say is "poor communication between academic staff and the department".

"It's been impossible for freshers," students' union president Barry McLaughlin said on Friday. "Even when everything is working well, it's hard for new students to find their way around a strange campus, but this makes it impossible. The second, third and fourth years were almost as confused."

In some cases, McLaughlin said, more than one lecturer and class turned up to the same classroom; on other occasions, no lecturer turned up at all.

Students were finally posted a corrected timetable to their homes the weekend before last, but it was a few days before it reached many students living away from home. Some parents faxed the posted timetable to their offspring via the students' union, but the situation was "still crazy" during the second week, the union said.

McLaughlin said he was concerned for students who will be examined next month on some of their modules. "By weeks 7 and 8 of term the pressure is really on and missing the first week of classes could really make a difference," he said.

A statement from the university said there had been a timetabling problem in the first week, which had been identified and remedied last Monday. Normal teaching was now taking place on a full schedule and arrangements were in place to ensure this wouldn't happen again.