It would help to know which codes are being reported, the best info is with the blink codes which you can read by following this procedure:
http://99mpg.com/mikestips/readingtheblinkcod/
Once the IMA refuses to charge, the condition will likely deteriate to a point where the 12V battery will not charge properly (12V fault light on dash) when you see that happening, beware, as you could be driving at night, and find that your 12V just dies, dash goes dark, and hopefully you will have a cell phone to call for help.
You can try disconnecting the 12 V for 30 seconds to reset the codes. If the codes do not come back right away, your pack is responding the the car trying to reset the SOC,but it will only be a temporary recovery, if the codes come right back, then you need to deal with the issue ASAP.
you can read this to better understand what is happening:
http://99mpg.com/blog/whatactuallygoeswr/
Good luck.
Mike