I lost my cable for my camcorder JVC GR-DVL300. I want to play the mini DV cassettes on it and record them to my computer.

The cable is a firwire 4-6 or 4-4 pin cable. Check your computer for the type of firewire socket it has. Most newer laptops have 4 pin.
These are available at most places that sell computer gear.

not available - the tapes are different widths for a start, and the two formats use different compression techniques. Adapters are available for VHS-C to VHS because the tape width and the recording format are the same.

Please use Mini DV Video head cleaning cassette as it seems video head is dirty / clogged in camera.

does anyone have any suggestions for us, or has anyone else ever experienced this same problem?

The heads are probably dirty. First you can try to let a tape run through from start to end and see if it cleans the head. then try running in reverse play scan. Next try a head cleaner tape if you have not yet. If these things do not get your picture back you should take it to a repair shop, I do not recomend taking camcorders apart for cleaning at home. Full size VCR's are ok to clean your self with instructions but not camcorders because they are vary easy to damage worse without experiance and proper tools.

If it is the JVC GR- DVL300 the manual is here. if not Give me the make and model and I will try to locate it for you.
http://books.jvcservice.com/Download/98451567/LYT0534-001C_.pdf

buy a cleaning cassette and play three times and then try to record .

My Sony camcorder wouldn't work with firewire either until I downloaded a fix at: http://www.microsoft.com/downloads/details.aspx?FamilyID=CA0F2007-18B5-4112-8BD6-8BF4BD3130B9&displaylang=en

Hope that helps!

Usually when the recording is started it takes around 10 to 15 seconds for the camera to recognise and display the duration of remaining tape, if you feel there is a problem, try using different brand tape.

This model is not supporting with pc when you play cassette only it is supporting with memory stick