IMAP Fetch hangs - message body parsed as tokens

Bug 735833 reports IMAP fetch hanging occasionally.

Similar problem occurred today. vm-imap-tokens shows a log like this:

 retrieve
 response #<marker at 110199 in IMAP mailhost.c 14:43:44>
 object #<buffer IMAP mailhost.c 14:43:44> "*" 110200 (atom 110199 110200)
 object #<buffer IMAP mailhost.c 14:43:44> "1669" 110205 (atom 110201 110205)
 object #<buffer IMAP mailhost.c 14:43:44> "FETCH" 110211 (atom 110206 110211)
 object #<buffer IMAP mailhost.c 14:43:44>
 object #<buffer IMAP mailhost.c 14:43:44> "BODY" 110217 (atom 110213 110217)
 object #<buffer IMAP mailhost.c 14:43:44>
   object #<buffer IMAP mailhost.c 14:43:44> 110219 (close-bracket)
 110219 (vector)
 object #<buffer IMAP mailhost.c 14:43:44> 110221 (open-brace)
 object #<buffer IMAP mailhost.c 14:43:44> "5441" "5441" 110225 (atom 110221 110225)
 object #<buffer IMAP mailhost.c 14:43:44> 110226 (close-brace)
 object #<buffer IMAP mailhost.c 14:43:44> "Return-path:" 110240
 (atom 110228 110240)

The (open-brace) is being recognized as a separate token (even though it is the beginning of a string of octets) because of a check added in revision 835.2.14 to allow non-numeric text in braces which gmail spews out occasionally. (Bug 926285). "5441" is obviously numeric, but there is probably a timing problem in recognizing it. Disabling the numeric check allowed the retrieval to proceed fine.