Cd- Writer not functioning at times?

My Acer CD-writer sometimes isnt recognized by the PC ... but at other it simply works smoothly ... i cannot understand the odd behaviour ...

initially i thought that its a driver problem .. but have checked the driver in Control panel and it doesnt have any error or anything on it ? secondly, i thought maybe its some hardware problem .. however, since at times the writer is functioning flawlessly .. it cant be that ???
i have Windowns 98 installed in my PC .
plz advise ?