Steps to reproduce:
[list: 74x9zzgc]

• Set the maximum number of quotes to a certain number (In my test, I ahad 5)
• Send a PM from user a to B, and quote that PM back to user A. Dont remove old quotes.
• Repeat the above step untill you get the error that there are to many quotes]
• The BBCode UID is in the quote tags still
  The result will like this:

  [quote="Paul":3optr1m0][quote="Paul":3optr1m0][quote="Paul":3optr1m0][quote="Paul"]dit is een test :P[/quote:3optr1m0]

  Dit is een test 2[/quote:3optr1m0]

  Dit is een test 3[/quote:3optr1m0]

  Dit is een test 4[/quote]

  Dit is een test 5

reproduced with at least 3.0.6 RC3 and RC4. Not sure about other versions.