i think what it comes down to is how it is listed on your transcript. some schools actually list lecture and lab (and their respective grades) separately on a transcript. if so, then list each separately with the proper number of credit hours for each. if not, then, as someone else mentioned, select 'combined lecture/lab' and just list the total number of credits given for the class.
you can enter the credit hours differently for each school, so don't worry that every school you attended did things differently. but you MUST enter the number of hours for each course exactly as indicated on your transcript--so if it says 1.5 credits for every single course on your transcript, then that's what you must enter. this is especially important because you attended different schools, and if you don't put the credits in properly, it will screw up the calculation of your overall GPA (i'm assuming that at least two of these schools were both for undergrad).
do you know how many 'regular' semester hours the 1.5 credits translates to? if it isn't indicated on your transcript somewhere, then call the registrar of your school--they can tell you this. then, when you first designate your schools, you will be prompted to select the credit system that institution uses. since the automatic 1.5 credits is unusual, i would select 'unit system' for this school. my school assigned 1 credit per course (regardless of time spent in class, labs, etc) and this is what i was told to do. i'm not totally sure if you can use the 'unit system' for 1.5 credits, but i'm thinking this is the best option for you. once you select this, you will be prompted to enter how many semester hours each unit is equivalent to, and then, when you enter your coursework for this school, it is now automatically programmed to list the proper number of semester hours for each course based on what you entered earlier. i hope i'm making sense. the problem is, if you've already entered your coursework, then you've already designated the school and you've already been through this screen--it only comes up the FIRST time you choose a school. i actually had to delete all of my undergraduate coursework and school and start over again because i too just entered 3 semester hours for each course and was later told that i couldn't do this, i had to enter exactly whatever it said on my transcript. yeah, it sucked.
there may be a way around this by now, though.
hope i was useful. good luck!