it's not possible to have a 5mb .ram file, it is possible to have a 5mb .rm/.ra file though. .ram files are text files containing links to the audio file(s) on the Internet somewhere (the m in ram stands for "metafile")
So is 5mb the size of the file itself, or is that the size of the audio file it links to on the Internet? I unfortunately haven't encountered your problem myself, I just tested Switch converting a 1 hour 45 minute .ra file to mp3 format. It took about 5 seconds to do on my 2.5ghz machine w/ 512mb ram.
We have had a few problems with Switch taking extraordinary long to convert .ram files containing PNM streaming audio protocol links. We found the solution was to manually edit the text file and change it to use the RTSP streaming protocol instead.