Often when I try to get my bard to perform fascinate or get one of my casters to buff an ally they run into melee range. My bard will perform fascinate at a distance early on in battle but later when I try to repeat it it'll run into melee range. Also, when I want my casters to cast buffs (greater invisibility for instance) they'll often run straight up to my front line fighters. If enemies are in the way is that considered breaking the "line of sight" or something? how can I tell if my caster has to run into melee range to perform a ranged spell?
You may be trying to cast spells that have a range of touch/short. You might try to read the actual spell descriptions to get the range listing and plan your tactics based on that. You might also want to get the the extend feat so that your buff spells last longer.
That was my first thought but I'm pretty sure fascinate for instance can be used at a fair distance. I started a battle with it once (at a distance) and tried to use it again later on (without my bard or the targeted enemy moving from the original positions) but the second time my bard ran straight into melee range.
The game is sometimes screwy. I have been able to cast inflict spells a a distance, usually before my cleric moves, but after that he has to close to touch. Not sure when/why this happens, but I just try to live with it.
This computer game allows spellcasters to cast touch spells at a distance up to the spellcaster's threat area from their target. Because of this, you can minimize the risk of spellcasters getting into trouble when casting spells during combat by equipping your spellcasters with a reach weapon (such as a longspear) and casting Enlarge Person on them before they cast a spell during combat. This will allow your spellcasters to cast touch spells up to 15 feet away from their target instead of the normal 5 feet.